This is one of the more interesting devices I've come across in my time, and it sat right under my nose, unrecognized, until recently.
My brother used this board to add memory to his PET. The cable leading from the top of the board plugs into the expansion connector on the right hand side of the PET 2001. The bottom of the board plugs into an S100 bus board. My brother had it plugged into a huge Vector Graphic Inc. board with space for 18 slot connectors, powered by a huge power supply from Forethought Technologies. Plugged into the bus board was a Vector Graphic 16KB SRAM board.
My brother bought this setup second-hand, and he thought it was normal PET memory expansion. Apparently the original owner had purchased it from a magazine ad in COMPUTE! or CURSOR magazine. It's a lot more interesting than just RAM expansion, though I don't know if it can use other classes of S100 devices.
Any info on this device, or on HUH? Electronics, would be appreciated.