1939 P08 with Nazi and Imperial markings

[Mac Cat]

The magazine bottom you showed is numbered 3095 and the suffix letter is "T", in my opinion.
The "+" symbol means that is was a spare or second magazine for that gun.

One can make some educated guesses on luger serial numbers by their block groups (suffix), but it is hard to narrow down to a particular month. Since the transitioned the year from 1939-1940 with the "Z" suffix, the gun was probably made very late in 1939.

The Imperial era is 1900-1918 (Germany is ruled by a Kaiser)
The Weimar Period is 1919-1933 (Between the World Wars)
The NAZI period is 1934-1945 (Hitler)

The Spread winged eagle was used from 1939-1945.

Below is an Imperial Eagle