This is a handwired Eurocard with a whole bunch of Eproms on it, mostly 2532 and some 2716. I don't remember ever having the bus for it and am not sure for which computer it is. But the address ranges on the Eprom labels match with the Acorn Atom. So it could me a variant of the "Schakelkaart" which allows for switching between the upper and lower set of Eproms.
Some cursory inspection of the B3/B4+ ROM contents show it is probably a BASIC and it contains the strings: "BYTES FREE" and "### COMMODORE BASIC ###". EXB4_9000 starts with "+++ EXBASIC LEVEL II /4.1A+++..(C) 1981 BY A.DRIPKE+M.KRAUSE".
At least the contens of the Eproms is now preserved for future generations.
Latest update: 2020-04-12