The lower of the two boards (the one not connected to anything) has the "LCC500" firmware on the EPROM (with Vienna stock exchange references) and has this jumper in the IC socket. The upper control board (which was fully connected) had the "LCC517a" firmware (with HEAG references). The lose EPROM was a second LCC500. Seems like they added the upper control board later and then updated the firmware at some point...