=== Expansion socket ===
The KC compact has a real connector compared to the P.C.B. edge connector of an English CPC6128. The connector appears to be a PC Card connector. This connector is not the same as the one on a German CPC6128.
The expansion connector has more pins; 58 compared to 50 on an English CPC6128.
The connector is a 'K1520 bus' connector which is present on all East German microcomputers. Some details about it can be found on the Wikipedia page for 'VEB Robotron' and some more here https://www.robotrontechnik.de/html/standards/k1520.htm (in German)
I am in the process of making an adaptor so that I can test CPC hardware on the KC Compact.