There were three different Waffenamts used on the 1922 as well as some eagle N commercial prrofs used on some very crude late wartime guns. Which do you have? (613, 103, 140, Eagle N)
I've also seen a couple examples with no Waffenamts, only test proofs.
I'm guessing yours is an earlier mid-range gun with a 140 WaA due to the wood grips and the fact that it still retains the "shoe" type trigger. Although I can't quite make it out, it appears to have a full 6 digit s/n in the 100,000 range. From what I have observed on examples over the last 40 years or so, the full 6 digit numbers seem to fall in blocks interspersed with 5 (or less) numbers with an "a" suffix, and to a much lesser extent in the "b" range.