Generalgouvernement stamps with the portrait of Hitler (Michel 75, 77-79, respectively) were overprinted with a large 2 or 4.
These stamps were issued from Koszyce. They were prepared for postal use in the Pińczowski district, briefly liberated by the Home Army, but re-occupied by the Germans, so they were never used. The stock was buried underground to prevent capture and they were recovered only in 1945, after the war. Since these stamps were buried, most of them have no gum left. There are only 56 complete sets possible, most of them disintegrated.
Overprints on Generalgouvernement stamps