Of German Interest,
By Richard Mahrholdt a gunmaker and author.

Handbuch für Waffenfreunde 1931 Innsbruck
This was followed by
Waffen-Lexokon 1937 F.C. Meyer München
The Waffen-Lexokon continued after the war and I may have a half-dozen or so. These are the “Gun-Digest” of German-Austrian gunmaking. The very best edition is the pre-war 1937 one, This is a fine gun book in any language. The later post-war ones kind of re-write gunmaking history in Germany but still interesting.

MP Sadly Deceased as of 2/17/2014