/vr/ - Retro Games

Sup /vr/, crossposter from /diy/ requesting backup. More of a hardware question than a retro vidya question, but I'm hoping there are some greybeards here familiar enough with this old hardware to call it.

Recently right-place-right-timed myself into a whole bunch of 80's era PC gear, some TRS-80's, a Commodore CBM 4016, some HAM specific RTTY gear, all sorts of goodies. Also snagged two still in box Amstrad PC3286 desktops (with peripherals and monitors in original boxes, one of which has never been opened.. 24 year old desktop, factory fresh in box.. FFFUUUU). I have been having stupid amounts of fun revisiting the hardware that this '82 model anon cut his computing teeth on.

Pic related is the only piece of kit I can't work out. It seems to hang off the back of the 4016 via a PCB edge connector, but there is nothing on it to describe what it does. Only markings on the board are "Micropro Designs 1982" and the label on the (open window!) EEPROM tells me little either.

Long shot as fuck, but do any of you recognise this?