Unusual proof

[CubanoLibre]

Newbie with question about a proof and a possible buy. I hope I'm posting on correct thread. This is a 1939/42 Luger with black grips with target circles. It has what appears to be a 'double' stamped proof on the L side of frame. What is that proof? I don't see any East German or Soviets proofs otherwise. The grips, I believe, are more commonly seen on VoPo East German (Soviet reworked) pistols. Nothing 'scrubbed' and no electro pencil marks. The R side of receiver markings do not match the markings in 'Standard Catalog of Luger,' Index #174 (pg. 210). Any help would be appreciated. ? Value??