There were two MMIs, Microcomputer Memories Inc. (hard disks) and Monolithic Memories Inc. (chips). As the label on your disk says, it was made by MMI in Van Nuys, California, a small company which didn't last very long. Most of the Hyperdrives I've seen had MiniScribe mechanisms, which have 2 LEDs on the front panel, green for power OK / ready, and red for activity. Miniscribe went through a bad patch where all their drives died within 20 power on hours of use, and they refused to warranty them, claiming that they all had been abused. Minscribe also was famous for shipping bricks in HD boxes to meet their quarterly shipments goal and allow management to meet their earnings target. Obviously, this strategy only worked for one earnings report. :

As a result, most hard drive companies at that time sourced drives from multiple manufacturers. It would not be unusual to see an MMI, Miniscribe, Microscience, Rodime or NEC drive in any of these early boxes.

MMI references are few - they didn't last long:

http://articles.latimes.com/1985-08-13/business/fi-1562_1_net-loss (higher sales volumes but still losing money)

http://articles.latimes.com/1985-06-04/business/fi-6678_1_position-of-vice-president

http://www.marketwatch.com/investing/stock/MMEM ( note that whole company is worth $824 today)