Hirose Cherry Precision Co., Ltd. (“Hirose Cherry”) was a joint venture between Hirose Electric Co., Ltd. (at that time the exclusive Cherry distributor in Japan) and Cherry Electrical Products that was formed in May 1973. Over their lifetime, Hirose Cherry sold at least four keyboard switch types: “Hirose Cherry MX”, “Hirose Cherry M8”, M85 and ML. ML may have been imported from Germany as it appears to be the standard design; little is known of M85, although M85 may have been a Hirose Cherry product that was imported into Germany.
Hirose Cherry MX and Hirose Cherry M8 are notable for sharing a keycap mount that is different to those of their Western counterparts. The following diagram shows the various 6 mm and 8 mm keystems; you can see that the Hirose switches share a common mount that is different from the 6 and 8 mm mounts used in the USA and Germany:
There are other differences. The slider planform of Hirose M8 is very different from that of most German-made M8 switches, although it has been seen in the German-made Basis 108 microcomputer keyboard for the unstabilised wider keycaps. The switch contacts in Hirose M8 are trapezoidal rather than the triangular and cylindrical designs of US and German switches. The 1988 part number schema for MX makes no mention of the Hirose keystem, either.
Curiously, the following was posted to the corporate history page of the former Hirose Cherry website:
|昭和58年4月||低背形キースイッチ(MDシリーズ)発売。||April 1983||Low-profile keyswitch (MD series) was released.|
|昭和58年4月||低背形キースイッチ(MJシリーズ)発売。||April 1983||Low-profile keyswitch (MJ series) was released.|
There may have been a suggestion somewhere that Japan got MX switches first; whether they would have got MX as early as April 1983 is not clear. However, it would not be implausible for the Hirose switches to have been a separate series from the German switches (since in Germany there seems to be no record of them), with MD and MJ being the Japanese series that correspond to M8 and MX (or MX and M8).
Sadly, no further details on these two series are known to exist.
There is another explanation. Hirose Cherry were granted patent JPS59828A in January 1984 for capacitive keyboards, and it is possible that MD and MJ series refer to variants of this, introduced in between the patent application and grant. Nothing is known about Hirose capacitive keyboards either, although Cherry in the US did introduce foam-and-foil capacitive keyboards in or before 1979.
Obtaining a Hirose Cherry catalogue would make this all clear, but so far nothing has been found, and Hirose have no information or are not prepared to find it if they do.