Luger ID .30 cal or 9mm

[Bill_in_VA]

Originally Posted by Josafoot

[...] I was more curious about what makes one think that this is an Alphabet Luger. Is it because of the Crown n marking's with the 4 digit serial number? That is what I am finding. [...]
I really liked the idea of the 9mm as an easier round to get and more universal.

An "Alphabet Luger" is a vernacular name for a commercial Luger produced by DWM in the mid-1920s. The Alphabet Lugers have a four digit setial number with a letter suffix (i.e. serial numbered in a military fashion instead a five digit serial number like previous commercial guns.) The c/N is a commercial/non-military marking that means the gun is nitro proofed, or safe for smokeless powder. You can find the same marking on many German commercial guns of the same period.
What makes one think your gun is an Alphabet Luger? That's like asking "what makes one think my Chevy Chevette is a Chevy Chevette?" The serial number, non-dated receiver ring, commercial proofs/no military proofs, no police sear/unit marks, .30 caliber. Read the stickys. They'll tell you. 😉