I’ve got a cherry later mauser model 1909 Argentine. Longer barrel than a regular Mauser but a very NICE rifle.
You’re right though, the 7.65 ammo is not really easy to find whenever you want it.
All the numbers on this rifle match and I’d guess it had to be a parade rifle since it’s in near perfect condition (except the Argentine crest has been buzzed off.)
If you can reload,then 7.65 ammo is easy.Cases are easily formed from .30-06 brass,and any bullet intended for .303 British will work fine.