It's an old card, originally developed during the BBC Micro era.
It's similar to the one on the right of the top photo on this page - Conqueror Design & Engineering Ltd - CNC control cards, stepper motor drives, CAD/CAM, CNC software, EaziCNC except it's not got the central orange connector at the top, or any of the bits to drive that stepper.

It basically takes a serial input from a computer, and runs it through a serial to parallel chip to drive everything.