i just thought i would put this info out here. it could be an urban myth and coincidence but heres my story.
many moons ago when these radios were current i had either an alpine or blaupunkt (im talking late 80,s?) the radio i was told wasnt working due to the code and being swapped onto another car.
i placed the radio in the freezer for a few days and lonand behold when it thawed out and i wired it up it worked! no code needed