I just acquired a 1991 560SEL with a Becker Grand Prix radio, removeable face plate, 10 disc chnager in the trunk. When my mechanic changed the battery on the car, we lost the radio to a "CODE" signal. No books or code cards can be found. Service records show the unit was installed in 1997. The s/n on the back of the face plate is 213011830952466841. My dealer said the code was 12242; however, the radio only accepts a 4 digit code. Anyone have another source for getting this code to unlock the unit? Thanks for all replies.