The Spanish refurbed an enormous part of their inventory for sale to Sam Cummings (correct my if I am wrong, that is what I remember at the moment).
They polished, sanded, refinished, reworked just about all aspects of the guns as part of the sale to make them "arsenal refinished". In today's market, they did far more harm than good. In the 1950's, Mauser's were a hard sell. To promote selling them, they were further "sporterized", like what we see here, cut barrel, bent handle, shortened stock.
Almost all of them (pre-68) have a caliber stamping somewhere prominent and visible.
You can also follow the "trail". Germany dumped most of their "older" and "obsolete" equipment to Spain because that was what they had on hand, and they could then replace it with newer K98k's. Someone here can tell you numbers, but large quantities of Gew 98m's were shipped to Spain along with other weapons.
I have a Mauser Oberndorf 1899 Gewehr 98 that is 1920 stamped, that was then converted to G98m, and then sent to spain, and then imported and mutilated. Someday I will return it to its G98m status. Neat rifle with a lot of history.