Mark – First this post should be in Axis pistols 1933 – 1945 German: German Mfg. (non-P08) Pistols & Holsters. Because a 1934 Mauser is .32 not.25 (6.35) caliber. You are lucky to have a Kreigsmarine marked variation. The 2 proofs are the Crown/U and the Eagle/N. The marking you describe as #42 on the Gunsworld link is a Crown/U sometimes called a double Crown/U. It means your example was made before 1940 when the German proof was changed to the Eagle/N. Regards,
NRA life member, NAPCA member
Aim small, miss small.