Cherry M1 (or M11, depending on how you interpret the M11-0101 drawing) is a customer-specific series created for HP as a drop-in replacement for Datanetics DC-60 series, with the dimensions matching those of DC-61-06. The most telling characteristic is that, unlike all other contemporary hard contact Cherry switches, M1 is single-pole only, with the internal arrangement adjusted to move the terminals to the centreline. In effect, M1 is an M9 switch rearranged to match the dimensions and keystem of DC-60. Switch travel is also reduced to 3.175 mm, to match DC-60’s travel of 3.18 mm.
DC-60 itself was introduced in 1973, primarily for Monroe, as a low-cost switch for high-end calculators. The M11-0101 drawing itself is dated November 1979, placing it well after DC-60 was introduced. M1 is however based on the tallest type (DC-61-05/DC-61-06), whose introduction seems to be between 1975 and 1981.
M1 is only known from HP keyboards, and has two discovered variants:
- Black: regular
- Clear (M11-0101): 95±25 cN: space bar (per the drawing), with customer part or request number 3101-0469
This customer part number is in fact that of a DC-60 switch. The HP 9825 service manual lists these three types:
|3101-2390||All Small and Normal Size Keys|
|3101-0468||Store, Continue, Execute (Double Size Keys)|
The Cherry keyboard for the HP 9835 (which uses M1 switches) had customer number 3101-0436-1 REV.G given to Cherry, which is clearly related. Sadly this later keyboard is missing from the HP 9835 service manual, which only covers the older chiclet type prior to the Cherry keyboard being adopted.
The 9825 service manual depicts one of the switches, which is clearly DC-60, and indicates that all three look the same, differing only in spring strength and lubricant used. The 9825 keyboard shown at Deskthority is an exact match for that in the service manual, and it is stamped “DNC” for Datanetics Corporation. It is the space bar switch part number from this keyboard that was passed to Cherry when M11-0101 was commissioned. (That is also the topic where, in 2014, Findecanor originally made the connection between M1 and DC-60, before DC-60 had been identified, hence not recognising the manufacturer stamp on the PCB.)
UncleFan sent me this photo from Brother Dragon (yab8433408) showing an HP keyboard with what appear to be the MX-mount DC-60 switches, alongside an M11-0101 for space:
Confusingly, these cream switches are (in the examples previously found for sale separately) the medium profile type, which makes them distinctly shorter than M11. At present, nothing more is known about the keyboard shown above.
The question of “M1” or “M11” remains unanswered. The part numbers do not follow the common schema. The part numbers follow the old system used with M41–M78, and being a German switch this would suggest M1, initial subtype, single pole. Being a custom series, Cherry Mikroschalter may have started allocating these up from M1. If this is true, it re-opens the possibility that MX really does denote series 10, with the Roman numeral X for 10. While it is true that a present-day unnamed German employee is noted for seeing a resemblance between these switches and “M10”, no explanation for “M10” has ever been found.