Hi Fred,
* Depends on what you have.
* "Doctor Bob VanM... conducted a survey in 1994 with the NAPCA membership. He had over 400 post-1933 Mauser produced Lugers reported. His summary was presented in the AutoMag issue dated 6/94, Pg. 66. My understanding of his conclusions are as follows.
* For the Mauser Army contracts:
- In general, there will be no known relationship for the "K", "G", or 1936's. Some 1936's after the "m" block, may include the Inside Sideplate Number(ISPN); but, some early 1937 S/Var. 1's are known to be correct and are without the ISPN. The transition seemed to appear in the 1936-1937 "m, n, o, p ,&/or q" blocks. A 40k S/N spread was noted as rather large; but, the best that could be obtained based on the data received. Also, sometimes, a single numeric or alpha character may appear on the I/Side of these early sideplates, usually in a horizontal attitude, and are thought to be factory (Mauser) worker marks.
- Again, in general for 1937-1938, the last 2 digits of the S/N will appear on the outside and the first 1 or 2 gun S/N digits will appear on the inside for 3 and 4 digit gun S/N's. In the case of a single or 2 digit gun S/N, the ISPN will always be the numeral "1" in a vertical orientation.
- Now for (S/42)1939-(byf)'42, the last 2 digits of the S/N will appear on the outside and the first 2 gun S/N digits + 1 will appear on the inside. As an example, gun S/N 1234 would have a "34" on the O/Side and a "13" as the ISPN throughout this time period. A "99xx" S/N'd gun would have "xx" on the O/Side and "00" as the ISPN (not "100").
* Mismatches are decidedly uncommon among Mauser Army pistols according to Mr. Van M.... Of the 295 reported, only 17 deviated from this pattern of rules(6%).
* Banner contract, Banner Police, '42 Portugese, "Ku", & Out-of-Sequence Assemblies were much less consistent.
* I don't recall the survey extending to WWI manufacturers/pistols(DWM or Erfurt P.08/LP.08's). I think the Weimar period would be a real mixed bag at best.
* Hope this helps.