NMB made a ton of keyboards. Their model numbers/names seem quite arbitrary and disorganized. They made a lot of OEM boards that didn't say NMB on them anywhere (except usually on the internal PCB, and the key switches would say either NMB or Hi-Tek if they were mechanical switches). You have to remember at this time, the IBM Model M was still the "standard" keyboard that came with an IBM PS/2, the standard Mac board was an Alps switch board, etc. so in those days it actually made sense for OEMs churning out cheap white-label PCs to spring for a mechanical board as a selling point.
I *sincerely* doubt the sticker is fake, fake keyboards are not terribly common, and you'd have to be crazy to fake keyboards manufactured by an obscure vendor that mostly sold to OEMs. If you want to be even more sure that what you have is an NMB keyboard, take off the plastic cover, the big circuit board that all the keyswitches are soldered to will probably have a big NMB logo on it somewhere, and there may be an NMB copyright notice on the controller IC.
NMB (Minebea Co., Ltd. of Japan) is still around and still making keyboards, but I think they mostly make scissor-switch boards for laptops - a lot of Lenovo ThinkPads and Dell Latitudes use them.
