Russian Luger?????

Don't be too quick to dismiss it as a fake. In Sam Costanzo's book, World of Lugers, he shows this mark- C.C.C.P. and says the following about it "U.S.S.R., Union of Soviet Socialist Republic, proof found on the chambers of captured or reworked Lugers for military or police use. Captured German weapons were reissued to Russian Stalingrad military forces. This proof was used 1941 through 1947." Locations noted: chamber and left receiver. This might be one of them.