Gestapo warrant/identification disc - similar to the Kripo disc, with the Reich Eagle on the back, but usually made of white metal.  Best regards, JR.

Gestapo Warrant/Identification Disc.

State Kripo Warrant/Identification disc, ?mid-1930s.  Hugo Boss could not claim credit for designing these - they had been around from way back in the 19th century in one form or other.  Those of the Nazi Period carried the image of the Reich Eagle on the other side.  Best regards, JR.

Krimalpolizei Warrant/Identification disc.

The whole story:
http://www.nortfort.ru/np/foto_tbt1_e.html
Nice set of photos of the recovery and cleaning and inside of  the tank :)

greetz,brummbar