rondog,
I got to this data from
www.mauserguns.com. From there I went to Mauserwimages.doc. (I can't make blue links). Here's the text:
1914 WWI era, Manufactured from 1914 to 1923, serial number range 13500 - 296000 (1 line address, “Mauser 7.65” stamping added on right side of slide around serial number 1625000, milled panel on right frame discontinued around serial number 277000, most examples in the high end of the serial number range will not have the Mauser Banner on the side plate.
Here's the text on markings, including the "1920"
Use markings
Use markings define the greatest number of variants as these pistols were exported all over the world and markings include acceptance, property
or inventory by a number of agencies. Some markings indicate export/Import, contract or military acceptance/inventory. The “Germany”, “Made in Germany (in Chinese)” and Portuguese contract mark (circle triangle) appear to be
factory applied (under the finish). Other markings like intertwined SK, intertwined WM, intertwined HD on the rear of the frame may also have been
factory applied. The commercial proof marks of other Countries such as British proofs, Austrian commercial proofs and Czech commercial proofs were stamped during importation. German military acceptance marks were stamped at the factory by government personnel. Agency property or inventory numbers as well as some import markings were engraved or stamped after the pistols left the factory. There are a good number of 1914 models that were used and marked by German police units. Examples stamped ‘1920’ were
so marked during the post WW1 era to identify it as property of the German government.
Vav