What do I have

I inherited a Luger and I like to know what model it is.

Here is a list of the markings that I found.

1. On the top of the barrel is stamped 1939.

2. A little further back where you normally find the Manufacturer's Trademark (like Spandau) is the markings S/42

3. On the left-hand side of the barrel is the number 6311 and 11 stamped on a couple of places.

4. On the right hand side of the barrel appears to Mauser military proofs for S/42 or 42 or BYF coded Lugers but only the first two stamps of stylized eagles match. The last stamp is almost like a Krieghoff proof that is like a stick drawn eagle (it looks like). Can anybody help me?