Blaupunked code

I am in the process of restoring another 1987 BMW 325i convertible and the battery went dead. A byproduct of that is the aftermarket Blaupunkpt model Cheyene CM 42 am-fm cassette shows "code" on the screen. Normally I can run a factory installed radio's serial number throught the local BMW dealership and come up with a code. Because this is aftermarket I'm lost!! Can anyone help???

Call Blaupunkt....