Hello
The Beocenter is a 7002 series, the external serial number is gone, the internal is 349067 .
The IC is a CD4066BCN, the add circuit is connected on the IC1 of the original module at pins 4 & 14, other cable are connected on the original board to take power and other two are connected inside the processor cable (purple and brown).
The add circuit seem to be not hand made...
Regards
ciao ciao
Eugenio