It's the chessboard LCD on the left side: https://www.schach-computer.info/wik..._System_MK_III

It's not neccesary, but would be nice to emulate. Chessclock and printer too, but I think the LCD is the most important of them. It can be done at a later point too, the base device is a good starting point.
*edit* ah, zu spat, Franz antworte zuerst. ;p