If you look at the outer edges of the radio itself you should see four 2mm
diam holes, two on each side.  Inserting a suitably sized wire/nail into
each hole all at once will release the locking mechanism.

Removal of the ashtray will reveal the access to the rest of the radio and
you can remove/replace at will.

With "heidelberg" well in hand the bosch boys should be able to give you the
unlock code.

Imagine, owning something you can't use because some ditzy liverwurst hammer
type decided that it was best to protect you from your own possessions.

Believe me if the boyz in the 'hood want the radio they don't check to see
if it works first.  If it can't be sold or traded it ends up on the side of
the road or like a friend's in his own trash can.  From which it was
retrieved and re-installed in short order, using of course the four nails
and no ashtray method.

p