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Brother Industries



Brother Industries, Ltd. (Japanese: ブラザー工業株式会社) is a Japanese manufacturer, founded in 1908.



Brother seldom if ever produced keyboards for off-the-shelf purchase, and it is possible that they did not even have any reference models. Brother keyboards were custom-produced for keyboard and typewriter manufacturers and for their own typewriters. In some cases, the Brother name appears inside, but quite often it does not. Examination of various keyboards suggests several ways that Brother can be confirmed as the manufacturer.

The Unisys PCK101-KBD keyboard is a good indication that Brother produced their keyboards in-house: this keyboard has not just a Brother-branded membrane sheet but also Brother’s FCC grantee code of B3Q. This keyboard bears the UL file number E57888 and the CSA file number LR94080; these codes in conjunction with a second CSA file number of LR53866 appear to represent Brother products and can presumably be used to identify Brother as the manufacturer without opening the keyboard.

Membrane keyboards may have the Brother logo present on the membranes. The presence of the logo is not necessary for identification, as the PCBs and membranes use a distinctive part number format that can be used as identification instead. In rare cases, a 556-series code is included on the outside of the keyboard.


Keyboard Switch type Brother code Membrane/PCB code Date Brother branding Reference Notes
Seikosha 8620 keyboard Foil-in-dome capacitive 556-601-01 None ca. 1982 Flickr The PCB is marked KB-31-3 and JCI-ALS
Epson Q603A Foil-in-dome capacitive None ca. 1984 Flickr The PCB is marked KB-33B-3 and GCMK-136EX
Burroughs B 25 K2 REV A (3675 6104) Foil-in-dome capacitive None ca. 1984 Flickr The PCB is marked GCMK-136EX and KB-70-4
IBM RT keyboard 556-712-01 ca. 1985 Bitsavers Appears to be an IBM 6298389 with different labelling.
IBM RT 6298389 Foil-in-dome capacitive B48U077-2 (PCB) 1985-03-25 Flickr PCB also marked GCMK-81X and KB-77-3.
Brother EM-721 Foil-in-dome capacitive B48V032-3 (PCB) March 1986 Typewriter KAref
KB-150 Plunger over conductive rubber dome sheet over PCB B518133-T (PCB) ca. 1986 Deskthority Logic board is marked B-482188-2 CMK-41X; connector board is marked B482187-2 GCMK-81X.
Brother AX-20 Plunger over rubber dome sheet over membrane B482063-4A ca. 1986 Typewriter KAref
Unisys T27-K5 (3753 0482) Rubber dome sheet over membrane, capacitive B518160-1 (PCB)
ca. 1987 Typewriter Flickr The PCB is also marked TCMK-77X. The F1–F3 LEDs are soldered to the membrane!
Unidentified Plunger over discrete rubber domes on membrane B48V097-3 (PCB) ca. 1987 Deskthority Incomplete set of photos; keyboard is from an unidentified device. PCB also marked JCI-N1S.
Unisys PCK101-KBD Rubber dome sheet over membrane 556-352 B48J240-1 (PCB)
ca. 1991 Membranes Flickr FCC ID B3QPC101
IBM 79F0167 Brother buckling spring B48J243-3 (PCB) ca. 1992 Flickr
IBM RT 6247440 Rubber dome sheeet over membrane B508195-3-A
1994-04-14 (PCB) Membranes Deskthority
IBM RT 6247440 Rubber dome sheet over membrane B508194-1 (PCB)
1994-04-14 (PCB) Membranes Flickr The Hitachi IC marked “4B16” suggests 1994 but the confirmed dates are 1992 and late 1993

Date markings

Most if not all Brother membranes, and many of the PCBs, show date markings that appear to indicate the month of manufacture. These dates are presented in an unorthodox and confusing fashion. PCBs and membranes so marked show two or three boxes, one per year, with dots indicating the months. Instead of adding a dot for each new month (as you see with the injection moulds for cases), it appears that one dot is removed per month. One would assume that these dots would be removed left to right, top to bottom, but the evidence points to the opposite: dots are removed right to left, bottom to top! The clue to understanding this process came from the Brother EM-721, whose PCB is marked as follows:

Steve Kuterescz dated the unit itself to March 1986 from its serial number, so that would rule out dot addition: the keyboard PCB’s date stamp must be from 1986 at the latest. The principle of dot removal would explain why the 1985 box is empty and the 1987 box is full. The one dot removed at the bottom right of the centre 1986 box suggests that January 1986 has passed, giving us a manufacture date of February 1986. The most recent chip on that PCB is from January 1986, so this would fit. Consequently, the marking below from an AX-20 seems to be May 1986:

It is possible that the removed dot is the active month, in which case the EM-721 board too is from January 1986, and the AX-20 board from April 1986.

The Brother-made Unisys PCK101-KBD is an unusual example of left-to-right, top-to-bottom dot removal, with both removal methods in use in the same keyboard. The membrane markings are the normal way round (starting from the bottom right) while the PCBs use a the opposite direction:

These dates will be June or July 1981. Curiously, there seems to have been no membrane production in 1990 from that tooling, as no dots have been removed for that year, as they were from the PCBs.