But it also had something odd...USB?!
Otherwise, the keyboard the same as an a keyboard I posted a couple months ago: NEC KBL-729EC-103
Also uses the NEC Oval Switches.



[url=https://flic.kr/p/DqWvj9]





Lol, that's why there's USB




Oh, and I've finally discovered who the CMK/GCMK numbers represent. As I thought, it's definitely the PCB fab. However, it's a special number associated with RU (UL), similar to FCC IDs for specific part certs. I think this may be the first board though that had the RU conveniently beside the number though

CMK is for Arisawa MFG Co. There is also a CMKG for Arisawa MFG, so that might be related to GCMK (no direct proof however).
Unfortunately, this puts me a step back in proving that Brother did Prototopre. I still don't have definitive proof that they OEM'd for Epson. Perhaps if we see some older (pre-1982) Brother keyboard devices we may be able to map the old product numbers.
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