I'm sorry, but I fail to see what you want. You have a drive with an MMI label on it. MMI was a real drive company. General Computer shipped MMI drives among others. You want a DNA match from your drive and an assembly line worker at MMI? I don't think anyone can help you, unless you can find the accountant or head of shipping at GC and have him look up your serial number, assuming the records exist.
Nixer, does your drive have an MMI label on it? Two people with MMI Hyperdrives would seem to prove that such beasties existed, and that perhaps MMI was the most reliable drive that GC used, considering how few Hyperdrives have survived.
I was VP engineering at a disk drive company (Micah) during this period and we and all our competitors shipped drives from multiple sources, wherever we could find a supply of reasonably-reliable mechanisms. 3.5" drives were brand new at this time and everybody was trying to ramp up production and shake out the bugs in their designs. It would have been foolhardy to have your company dependent on a sole source.