It means the action of the rifle was made by Mauser or copied by someone.
More than one Mauser
try: k98k.com
Mausers manufactured for Argentina and the Ottoman Empire (prior to its dissolution - later Turkish Mausers used the 7.92x57 cartridge) used the 7.65x54 cartridge.
There are various numbers, including the serial number, proofing marks, and caliber. Most Spanish Mausers were chambered in 7X57.
The Mausers rifles, such as the Kar98K, fire this round.
Some Mausers
They're in the same class as cartridges such as the .308.
Mausers of the world by rober w ball
Mausers of the World by Rober W. Ball is a good place to start
Mausers made for Argentina and the Ottoman Empire used a 7.65x54 cartridge.
Contact the factory, go to the library, find a copy of Mausers of the World.
7.92x57mm, better known as 8mm Mauser. Same caliber as the German military's Mausers.
You need to specify what model specifically. Mausers were manufactured at many arsenals with varying degrees of quality.