Cherry common part number schema
Having obtained the M9 part number schema from Ed Ferraton at Cherry USA (whose office is a goldmine of valuable data), a number of questions were cleared up, and I decided to present the details here. Since a number of Cherry’s switch series share the same part number schema, I have decided to include them all together.
- Revised part schema for keyboard switches
- Additional notes
- Character positions:
This page is based on a variety of literature, as well as e-mail conversations with Cherry Germany and Cherry USA. Most of the literature is present on the Deskthority wiki under Cherry catalogues. In addition, the following documents were used:
- Cherry M9 part number schema provided by Cherry
- 1985 Cherry keyboard switches advertisement in the 1985–86 Electronic Engineers Master catalogue, volume 2 (mentioned by LGR in this YouTube video on the Cherry KXN3-8451) (PDF extract)
- Hirose datasheets on M8, MD, MJ, MX and M85 (which cannot be shown here)
Documents yet to be obtained include:
- Press releases and other introductory information on any Cherry switch type (giving such information as the official introduction date of “M7” (before it was called that) as well as the extent of the MX series at its introduction)
- Literature providing part number listings for Cherry MY actuators and an explanation of the MY schema
- Part number schema for Cherry ML
- Literature and schemata for the Hirose switches we actually encounter
In an ideal world we would also find literature providing a rationale for each of the unexplained choices offered with each series, such as why you would choose a bar versus tee keystem with M7 switches. Cherry at the time would have known why each option existed and who chose it and why, but such knowledge is likely now lost forever.
Absent from this page is Serie M7, as it pre-dated the revised schema; see the M7 schema page for an attempt to reconstruct the schemata for gold crosspoint and Serie M7.
Revised part schema for keyboard switches
Starting from Serie/Keymodule M8, Cherry introduced a revised part number schema, in the form:
The individual positions denote:
- “Keymodule”, i.e. keyboard switch
- Series: 8, 9, D, J, X, Y and L (M8, M9, MD, MJ, MX, MY and ML) are the series known to use this schema
- Contact design, rating and material
- Switch characteristics
- Actuation force and switch behaviour
- Keystem design
- Standard features: LED presence and colour, and presence of jumper or diode (mutually exclusive)
- Additional characteristics, often series-specific, including presence or absence of fixing pins, inclusion of factory-supplied keycap, SMD LED support and terminal plating
An explanation of the various codes is given below. Note that not all variants are confirmed to have gone into production. Further, the details below only represent current understanding based on documents discovered to date.
Cherry appear not to have given their keycap series official designations. The following designations appear in catalogues:
- 12 mm
- Flat/sloped profile, spherical, 12 mm tall; used with M7, M8 and M9 (with appropriate keystem selection), and made of Tenite
- 6 mm
- Flat/sloped profile, spherical, 6 mm tall; used with M8 and M9 (again with appropriate keystem selection), and made of ABS
- 8 mm
- Flat/sloped profile, spherical, an 8 mm tall derivative of the 6 mm keycaps, that is used with MX, but also mount-compatible with M8 and M9 switches designed for 6 mm keycaps (in the 1994 Keymodule MX brochure this is referred to as “Standard type”); the specifics of 6 mm versus 8 mm keycaps and keystems are far from clear at this point
- Cylindrical type
- Cherry’s standard cylindrical keycap series used with MX switches (abbreviated “Cyln” in the 1994 Keymodule MX brochure); this is described as 7 mm (in fact 6.9 mm), which is the height of the front centre of a row 3 keycap (the maximum height is not given, but row 1 comes out at 9.8 mm tall)
Known keycap mounts:
- Bar, for 12 mm
- Generally, bar and tee mount switches are used with cruciform mount keycaps, which permit the switch to be orientated as needed for the PCB routing or other preference. However, a HAL KB2100 keyboard was found with a bar mount space bar, and the space bar switch was modified to fit the keycap, indicating that some keycaps specifically required a bar stem and for the stem orientation to be correct. Bar mount for 12 mm keycaps was found on M7 and M8 switches; M9 also supported 12 mm keycaps, but the mount used has yet to be seen (the part number schema drawing implies tee or cruciform mount). Cherry referred to this mount as “straight”; “bar” is used here to avoid ambiguity between straight mount and vertical keystems.
- Tee, for 12 mm
- This is a variant of the above, and generally shares the same keycaps. This mount was found on M7 switches; it is unknown which 12 mm variant was used by M9 switches as this was not depicted in the catalogue.
- Cruciform, thick-vane
- This was used by Burroughs in the early 1970s with type M51-0129 and later type M51-0131 (which seems to be a revision of the same design). It is superficially similar to the MX mount but will not accept MX keycaps. The M51-0129/0131 drawing specifies the vane thicknesses as 0.051±0.002″ and 0.045″ which matches a specimen of M51-0131. The mysterious M91A-1GBR custom M9 type from Bulgaria also uses this mount; its stem measures instead 0.055″ and 0.045″, which is marginally out of tolerance, but both accept Commodore 64 keycaps.
- Cruciform, medium-vane
- This is chiefly found in Royal/Triumph/Adler typewriters on M9 switches. It bears superficial resemblance to the 12 mm mount, but 12 mm keycaps fall off, and typewriter keycaps do not fully fit onto 12 mm stems.
- Cruciform, thin-vane
- Used with 6 mm and 8 mm spherical and 7 mm cylindrical keycaps. These have a short (ca. 2.2 mm) keystem in M8 and M9 switches, and a taller (ca. 3.6 mm) keystem in German MX switches. This is referred to as “Cherry MX mount” even though it pre-dates Cherry MX.
- This is similar to the 8 mm mount, but the overall width and depth are around 3.4 mm rather than the 4.0 mm of 8 mm mount, and the keystem is 0.1 mm shorter at 3.5 mm tall. This mount is used with not just Hirose Cherry MX, but Hirose Cherry M8 also. As a consequence of the smaller dimensions, US and German keycaps will fit on Hirose switches, but Hirose keycaps will not fit on US and German switches.
The following diagram shows a comparison between the stem heights of M8 and MX switches from the USA and Germany, Hirose Cherry (M8 and MX), and the “MX” mount found on M94A-18NI:
The cross section difference between German Cherry 8 mm mount and Hirose Cherry mount is given below. 6 mm mount in M8 switches is not quite the same as MX 8 mm mount, but MX keycaps can be fitted to 6 mm mount M8 and M9 switches.
Cherry’s original keyboard switches (introduced ca. 1970) were not given a formal series name. At some stage, a second set of part numbers was created, quite possibly in parallel by Cherry Germany. This series became known as Serie M7. When Cherry introduced new switch series, they followed on from this. While Serie M7 continued the part numbering format of gold crosspoint, M8 and M9 adopted a new format, that has continued to be used since, and “M” came to formally denote “Keymodule”. Later series numbers were assigned letters, perhaps to allow them to fit into this exact schema.
Switch series are described as “Serie” (e.g. Serie M8), “Keymodule” (e.g. Keymodule M8), “Model” (e.g. “Model MX”) or “Technology” (e.g. “MX technology”) depending on the literature.
Known switch series that use this schema are (at the time of writing):
|8||Cherry M8, (Hirose) Cherry M85|
|D||Hirose Cherry MD|
|J||Hirose Cherry MJ|
The rationale for the series designations is not known. MX suggests M9+1, but Cherry Germany seemed to think that M10 existed, and although part M11-0101 exists, it is not clear whether this is M1 or M11 series. In terms of published catalogue products, M9 was seemingly followed by MX, then MY seems to have simply followed alphabetically from MX. ML possibly denotes “low-profile”, with L not following alphabetically from Y.
3: Contact design
Contact design covers both the physical construction of the switch contact points as well as the material used. In most series, there is only one defined contact option and this field is simply left as “1”. However, M8 and M9 share the same complete contact design, and likewise share the same value sequence.
Little further explanation of the contact designs is given in any catalogues. Cherry seem to assume that customers already have a good understanding of switch contact operation and robustness.
Cherry did illustrate the cross section of the gold crosspoint contact as follows, in the the 1973, 1974, 1979 and 1982 catalogues:
US catalogues cite the switch contact material as “W/E Alloy #1” or simply “W/E #1”, denoting Western Electric Alloy #1 (69% gold, 25% silver and 6% platinum). If the manufacturing process is the same as any of the 1930 Western Electric patents, then the contact material is a solid wire formed into the surface portion of the switch contact. Hirose Japan also used Western Electric Alloy #1, given also as “W/E #1” in datasheets. Cherry Germany appear by and large to have used other alloys; M9 did offer this same composition (as M93), but the only catalogue to list M9 switches does not name the alloy.
M94 uses AuAg10 at 3 µm, which indicates that the “4”-type contacts are merely gold plated, while the others are assumed to be solid metal per the diagram above. Curiously, the 1982 catalogue—which does not mention the alloy composition at all—only covers M7, M81 and M93, which are all triangular-prism contact, even if they do not use the same materials (M81 is AuAg26Ni3).
M8 and M9
The Cherry Keyboards and Switches Catalogue 1982 offers limited options for switch contacts. For M8, only type 1 is offered, and for M9, only type 3 is offered. No further details on the switch contacts are given, apart from the structural diagrams, as previously noted. The Keymodule M8 brochure offers additional options for M8, while no Keymodule M9 brochure has ever been found. The full range of M9 contact types below comes from the part number schema from 1985.
Cherry M85 appears to be a completely separate series from M8, which for some reason was lumped together under M8 by using contact type 5. As M85 has yet to be observed, it is not known whether it really does have a 5th contact type, but the Hirose datasheet gives it as W/E #1 alloy, the same as Hirose M83, MD4 and MJ4. It has “N” as the keystem code, indicating Japanese custom parts, and in April 1987, Hirose Cherry mentioned the introduction of M85 on the former Hirose Cherry website (www.hirose-cherry.co.jp) (“昭和62年4月センターLED式照光式押し釦スイッチ(M85シリーズ)発売。”). This timeline entry was present in 2001 on the Hirose Cherry site, but Cherry themselves did not mention any old switch types by the time that the Wayback Machine found their site; from 1998 onwards (the extent of the archives), Cherry’s website only mentioned current products, which at that time were MX, ML, M81 and M84 series.
Hirose MD4A and MD4A appear to also use W/E #1 alloy with layered prisms, which should make these MD3A and MJ3A. As no confirmed M93 switch has been seen, it remains to be seen whether M93 and M83 share the same steep trapezoidal contacts.
Contact style 4 is easily recognised by being cylindrical in nature, with the cylindrical contact bar only 0.25 mm wide. Contact style 3 remains unconfirmed. Contact styles 1 and 2 are plain triangular prisms, around 1.0 mm wide, 1.4 mm long, and 0.5 mm tall. The following diagram shows very approxiate colouration:
The gold alloy prisms are bright and only faintly gold-tinted. Seen through a loupe under bright light, just the contact edge tends to shine somewhat golden, while the rest of the surface can look silver-tinted. However, in comparison with M82, it becomes relatively clear which is gold alloy and which is silver alloy:
The photos above were taken from sample parts preserved by Cherry USA, who graciously provided them to UncleFan for his collection.
|1||AuAg 26 Ni 3 (71% gold, 26% silver, 3% nickel)||100 mA/28 V||M8 only|
|2||AgPd 30 (70% silver, 30% palladium)||100 mA/60 V||M8, M9|
|3||Au 69 Ag 25 Pt 6 (69% gold, 25% silver, 6% platinum)||100 mA/28 V||M9, Hirose M8 (same material but rated as 10 mA/12 V maximum)|
|4||AuAg 10, 3 µm (90% gold, 10% silver)||10 mA max./12 V max.||M8, M9|
Contact designs (which UncleFan decoded) are given only as geometric shapes that approximately indicate the shape of the switch contacts. For the triangular prism contacts, this is sufficiently accurate. For the cylindrical contacts, the cylinder is much smaller and the stationary contact sits on a highly embossed terminal. More confusingly, Hirose M8 switches have trapezoidal contacts that do not match any of the German types (including those of MX and M7). It remains unclear whether Hirose MX uses the same contacts, as there are no photos that are sufficiently clear.
MD and MJ
MD and MJ are derived from M8, but are documented to use keystem code 4 for the alloy covered in code 3. There are simply too few details available to understand this more clearly.
|4||Standard layered prism, W/E #1 (69% gold, 25% silver and 6% platinum)|
Cherry MX only has one official contact type, type 1. In the 1988 part number schema and the 1994 Keymodule MX brochure, it was listed as AuAg 10, rated at 10 mA and 12 V maximum (AC or DC). This is the same rating as M8 and M9 type 4, and the contact points were the same cylindrical form as M8/M9 type 4. However, in an earlier datasheet marked July 1985, the maximum voltage was given as 5 V. In the advertisement allegedly published in 1984, the maximum figures are given as: 125 mA during switching, 500 mA carrying, and 28 V.
According to Cherry Germany, the contact design changed in 2007; modern MX switches have prisms, but the change in design did not result in revised part numbers. A 2006 unknown catalogue section on Keymodule MX offers no specifications at all, while the the 2010 Cherry switch catalogue gives the contacts solely as “High-quality gold alloy”, with the voltage and current ratings unchanged. The Keymodule brochure from 2002 however (which covers only MX and ML) gives the ML contacts as AuAg 10 but the MX contacts solely as “High-quality gold alloy”. Recent and current Cherry datasheets continue to cite the 10 mA/12 V rating and “High-quality gold alloy” contacts.
The 1988 part number schema allows also type 5 for “Special”.
When damped MX switches were introduced, this position was also used to indicate damped switches, with code 3. The switch contacts presumably remain unchanged.
|1||AuAg 10, 10 mA and 12 V maximum|
|3||As above, but with dampening integrated into the slider|
MY only has type 1; this may be a dummy value considering that MY modules do not have switch contacts.
MY only has type 1. Modern datasheets cite “High-quality gold alloy” the same as Cherry MX, while the Keymodule brochure from 2002 gives the ML contacts as AuAg 10. Cherry ML is 10 mA and 12 V AC/DC maximum, which is the same as Cherry MX.
4: Switch characteristics
The final position before the hyphen denotes the characteristics of the switch, in particular the number of contact pairs present in the switch, and the operating function of the switch. This position is not consistent between series: for M8, it also indicates whether the switch is covered or uncovered, and for M9 the switch configuration is also carried over into the next position.
Contact characteristicsGeneral descriptions of switch characteristics are covered on a separate page.
Cherry M8 confusingly uses this position to cover operating force and whether or not the switch is covered, in addition to the contact configuration.
All M8 types are momentary.
|Value||Configuration||Shell||Linear force||Tactile force||Notes|
|A||SPST-NO||Uncovered||70±20 cN||105±30 cN|
|C||DPST-NO||Uncovered||90±30 cN||95±30 cN|
|E||SPST-NO||Covered||70±20 cN||105±30 cN|
|F||DPST-NO||Covered||90±30 cN||95±30 cN|
|G||SPST-NO||Uncovered||95±30 cN||N/A||For space bars|
|H||SPST-NO||Covered||95±30 cN||N/A||For space bars|
|I||DPST-NC||Uncovered||?||?||No forces are ever given|
|S||1.5 mm travel (Hirose M83)|
Note that the switch configuration is also included in part in the subsequent position.
|D||DPST-NO/NC break before make (suitable for wiring as SPCO)|
|E||Double action (described as “1 N.O + 1 N.O overtravel”)|
MD and MJ
There is no data on these series.
Officially MX only offers type A, being SPST-NO. The schema also gives C as “special”. The switch patent depicts DPST, which is an option that Cherry appear to have foregone in order to make room for LEDs (which is peculiar considering that the factory-fitted LED version uses a different shell anyway). As Cherry MX Low Profile piggybacks onto the MX schema by occupying MX1B, this suggests that MX1B was never used historically, but the loss of data following the ZF takeover means that MX1B could have been used previously, and then forgotten.
MY leaves this as “A”, as there is only one operating mode: SPST-NO momentary progressive rate.
ML switches are divided into “Lowest profile” (A) and “Robust” (B). Both A and B types are momentary SPST-NO; the difference is simply the height of the switch. Type B switches have a taller slider and guide shaft, which may help combat the binding for which the switch is infamous. Type B is now discontinued and it was rarely encountered: all G84 keyboards discovered to date use type A switches.
5: Force and behaviour
Format: numeric or (with MX) alphanumeric
For M8, the force figures are given under the previous position. This position only indicates the type of force curve offered.
|4||Tactile feedback in compliance with West German Postal Service specifications|
Note that the number of poles is redundant against the previous position, which already codes this characteristic.
120±30 cN (stage 1), 500±100 cN (stage 2) (1982 catalogue)
85 cN (stage 1), 400 cN (stage 2) (1985 schema)
|4||Momentary||Single||120 cN||Space bar|
|5||Alternate||Single||82 cN||Keystems 1 and 2 only|
|1||50〜80 gf (i.e. 65±15 gf)|
|1||50〜90 gf (i.e. 70±20 gf)|
MX was originally divided between linear and tactile types, with linear types given a numeric code, and tactile types given an alphabetic code. However, Cherry MX Red was mistakenly given “L”, putting it not only in the wrong set, but also some way past the end of the existing codes!
Only confirmed Cherry MX types with known part numbers are noted here. Only limited variant details are given here.
|Value||Action||Type||Weight (actuation)||Travel||Keystem colour||Notes|
|0||Momentary||Linear||50±17 g||4 mm||Unknown||Hirose MX|
|1||Momentary||Linear||60±20 cN||4 mm
3.7 mm (damped)
|2||Momentary||Linear||80±25 cN||4 mm||Grey 37||For space bars|
|3||Alternate||Linear||60±20 cN||4.2 mm||Black (older)
|4||Momentary||Linear||52±15 cN||4 mm||Colourless|
|5||Momentary||Linear||45±15 cN||3.4 mm||Silver|
|A||Momentary||Tactile with hysteresis||70±20 cN
(previously 75±20 cN)
|4 mm||Colourless (early)
|B||Momentary||Tactile with hysteresis||105 cN||4 mm||Grey 36||For space bars|
|C||Momentary||Tactile||55±20 cN||4 mm||Colourless|
|D||Momentary||Tactile||80 cN||4 mm||Grey 39||For space bars|
|E||Momentary||Tactile and clicky with hysteresis||50±15 cN||4 mm||Blue|
|F||Momentary||Tactile and clicky with hysteresis||70±20 cN||4 mm||Green||For space bars|
|G||Momentary||Tactile||45±20 cN||4 mm||Brown|
|L||Momentary||Linear||45±15 cN||4 mm
3.7 mm (damped)
The actuator for “type 3” MY switches has 2 in this position. The meaning of this code is unknown.
Cherry ML only has one type and weight, tactile with 45±20 cN actuation. This is given code 1.
Format: numeric (standard keystems), alphabetic (country codes)
There appear to be two keycap mounts for old Cherry switches: 6 mm low profile (for M8 and M9) and 12 mm high profile (for M7, M8 and M9). The keystem designed for 6 mm keycaps became the keystem on MX and MY switches, albeit reprofiled for 8 mm keycaps. Cherry ML on the other hand has a unique mount, one that Kailh curiously chose not to re-use for their similar switches.
The schemata for both M9 and MX use this position for non-standard types. As this is the keystem position, the implication is that it denotes non-standard keystems (e.g. Olympia, Alps). However, all non-standard MX types discovered so far appear to differ only in weight, not keystem (the one M9 type discovered with a custom code appears not to be different in any way). As such, country-specific codes in this position seem to denote any non-catalogue design. With both MX and M9, the seventh and eighth positions change to alphabetic and appear to denote the customisation. (Both the MX and M9 non-standard types have used country code “G”.)
No other type is yet known to follow this pattern. However, M85 uses this position in a curious way, as previously mentioned.
The special types are divided by country; these same codes were given for both M9 and MX:
|United States||W||C, F|
|United Kingdom||U||K, E|
Perhaps the choice for the USA, of “W”, denotes Waukegan, Illinois, where Cherry’s headquarters were located.
As of 2018, the official table on the Cherry MX Developer Page gives only Germany, as G, D and H. D and H are still marked as reserved.
Keystem codes are partially redundant with the switch configuration in the previous position, rather than being specified orthogonally. The 1982 catalogue gives types 1–7, while the undated Keymodule M8 brochure only offers 1, 3, 5, 6 and 7.
Types 1 and 3 differ in the cross section shape of the keystem but take the same keycaps, and the difference between the two types is not explained. For unexplained reasons, only the type 3 slider can be used with 1B and 1A+1B contact arrangements (2B is seemingly not restricted in this manner).
Types 2 and 4, missing from the M8 brochure, are both 12 mm, 0°, covered-switch keystems and appear to be a redundant pair. The 1982 catalogue where they appear provides no elaboration of any kind.
Outline drawings indicate designs that have not been seen but approximate or unclear details exist in catalogues.
|1||6 mm, 0°||Uncovered|
|2||Not seen||12 mm, 0°||Uncovered|
|3||6 mm, 0°||Uncovered|
|4||Not seen||12 mm, 0°||Uncovered|
|5||6 mm, 0°||Covered|
|6||12 mm, 0°||Covered|
|7||6 mm, 7° (not seen)||Uncovered|
|N||Uncertain||Used by Hirose M83|
Hirose M83A and M83S are depicted with a keystem that is 3.5 mm tall (per Hirose MX) but lacking the diagonal grips that are not only found on Hirose switches, but depicted on the same datasheet for MD and MJ series. The overall appearance of the M83 mount is that of MX, while MD and MJ are clearly shown as Hirose mount, with a narrower stem. The details on Hirose M8, MD and MJ are simply too vague, and no discovered examples appear to match anything documented.
The Keyboards and Switches Catalogue 1982 catalogue gives M9 as accepting standard 6 mm and 12 mm keycaps. However, M9 permitted far more options than the catalogue offered. The 1985 numbering schema offers various keystem options that are not explained, but one can reasonably assume that “CM” denotes “Cherry Mikroschalter” and indicates standard Cherry keystems (6 mm and 12 mm), and that “TA” denotes Triumph-Adler and indicates the keystem forms used in Royal/Triumph/Adler electric typewriters (those using M9 switches, as MY seems more common). Only the “CM” types are found in the 1982 catalogue. Presently the meaning of “L-T” remains a mystery.
The descriptions below are given verbatim as their meanings are not confirmed.
|Value||1982 catalogue||1985 schema|
|1||12 mm, 0°||CM Standard
|2||12 mm, 10°||CM Standard
|7||6 mm, 0°||lowpro-keycap
TA 7° bent
|9||6 mm, 7°||Absent|
|G||Special||Used by M94A-1GBR, with a thicker mount than 12 mm or TA|
German documentation (up to the present day) only recognises one keystem design, which is coded “1”. This is the standard 8 mm stem. Hirose used “N” for the only known documented type, MX1A-0NNN, where N is a country-specific code for Japan.
In addition there is at least one other mount. Cherry MX Olympia Linear Clear has a keystem that is almost the same as standard 8 mm, but it does not quite have the same fit. Additionally there are completely separate mounts, including Alps mount and whatever mount the mis-named Cherry MX Alps Clear uses (which is not Alps mount). None of these additional mounts are known from a single piece of equipment and none of these mounts are proven to be from authentic Cherry parts (whether made by the US or by Germany).
There are also a number of special types with “G” codes, many of which are confirmed by Cherry. Those found so far only appear to differ in weight.
|1||Standard straight for cylindrical and 8 mm keycaps|
|G||German-made custom types|
All MY switches encountered to day use Cherry MX (8 mm) mount, and the only known part number (for the “type 3” actuator) has 1 in this position.
ML switches only have one mount, specific to ML switches, and it is given code 1.
7: Standard features
Format: alphabetic (except for 0 denoting “none” in M8)
Where the keystem code in position is standard (numeric), the meaning of this position is as detailed below. Where the keystem code denotes a country-specific part, then position 7 carries the first character of the custom part code.
M8, M9, MX, MY, ML
|0||No LED (incorrectly given as “O” in the M8 brochure)||M8|
|N||No LED (M9, MX), diode (MX) or jumper (ML, MX)||M9, ML, MX, MY|
|R||Red LED||M8, M9, MX|
|G||Green LED||M8, M9, MX|
|Y||Yellow LED||M8, M9, MX|
|S||Super-bright red LED||M8|
|Z||LED shell with no LED fitted||M9 (this is the de-facto design of M8 open and MX)|
|J||Internal jumper||MX, ML|
Note that MY is only known to use “N”. Also, for ML, the November 2013 ML1B-xxxx datasheet posted to the Cherry website only offered ML1B with a jumper, while the jumper was optional for ML1A per the July 2015 ML1A-xxxx datasheet.
MD and MJ
8: Additional characteristics
Format: alphabetic (except for 0 denoting “none” in M8)
M9, MX and ML use this position to indicate whether or not fixing pins are provided. As M8 switches are all PCB mount, they use this position for keycap colour. MY uses this position for an unknown purpose. Where the keystem code in position is standard (numeric), the meaning of this position is as detailed below. Where the keystem code denotes a country-specific part, then position 8 carries the second character of the custom part code.
Since all M8 switches are PCB-mounted, this position indicates the colour of keycap supplied with the switch. One assumes that this is intended for companies who wish to provide their own engraving, etching or pad printing of the legend.
The options are:
|0||No keycap (incorrectly given as “O” in the M8 brochure)|
|S||Black keycap (presumably denoting schwartz, as B is already used for blue/blau)|
Curiously for Cherry, the shades and hues are not stipulated. In particular, the brochure does not indicate whether the shades of blue, grey and green are light or dark.
M9 doubles up this position to also cover the plating on the solder terminals in addition to whether or not fixing pins are provided.
|Value||Fixing pins||Movable contact terminal||Stationary contact terminal||Notes|
|M||With pins||Bare||Bare L49||M94 only|
|I||No pins||Bare||Bare L49||M94 only|
|L||No pins||Silver-plated||Bare L49|
The above table is an interpretation of the terms used in the M9 part number schema. Cherry refer to the “contact blade” and “contact bracket”, which I am taking to refer to the movable and stationary contacts respectively, along with their solder terminals. So “contact bracket L49 blank” (for example) appears to denote that the stationary contact is made from L49 alloy and that its solder terminal is unplated.
MD and MJ
MX switches traditionally used “W” for switches with fixing pins, and “N” for switches without fixing pins. With the invention of SMD LED support (where the LED slot is replaced with a clear lens that sits above an SMD LED on the PCB), an extra pair of letters was created: “A” denotes plate-mount SMD RGB switches (without fixing pins) and “B” denotes PCB/plate-mount SMD RGB switches that include fixing pins.
The 1988 part number schema for MX indicates that MX1A-__NW is not possible: that is, if the switch has pins, it must include an LED, jumper or diode. No reason is given for this, nor does it make sense. Further, MX1A-11NW is available for sale as surplus parts.
|N||No pins||Black (fits monochrome through-hole LED)|
|W||With pins||Black (fits monochrome through-hole LED)|
|A||No pins||Translucent/transparent with lens for RGB SMD LED|
|B||With pins||Translucent/transparent with lens for RGB SMD LED|
MY “Type 3” actuators have a C in this position; no explanation is known. They do have pins, but of a different design.
All ML switches are PCB mount, so all ML part numbers end “W”.