It was one of the removable storage systems that were all the rage at the time. Back around 1993 there were two main competitors: SyQuest, with their 44 and 88MB disks and drives, and Iomega, with their Bernoulli drives. From what I've read, Bernoulli drives were the better technology, as they were more reliable and durable, but they were also a lot more expensive.

Just whatever you do...just make sure you get the drivers for the Bernoulli drive and the graphics tablet off the HDD before you format it. Its ok to get software off old hard drives, especially since in this case you'll need it to use some of the peripherals (which may or may not still have the driver disks with them)...just as long as you don't keep any user-created data.