[crash]

Unstamped main cases were availiable over the counter for sale to the public, or for use as warranty replacement part...
Most O.T.C. cases have a small cc with a single number after(cc9) and a 5 digit serial number in the same area...
Early 660 O.T.C. cases (1968) some time won't have the cc or the serial number at all...
You don't see unstamped 660 cases often but their out there... I have several unstamped and 25 or more 660 and 661 O.T.C. cases with the cc and the serial number...
Hope this helps... Crash