Please Help me date my luger

[drewdog]

Hey guys, I appreciate all of your interest in helping me date this gun. I'm doing my best to answer the previous questions. My dad tells me its a 30 cal luger. The wood bottom clip number is 6503 with a couple markings on it. One marking looks like a + sign, and I don't understand the other. I am adding additional pics to show you all. Thanks again, and Dwight I don't see the crown proofs that you mentioned.