There are various numbers, including the serial number, proofing marks, and caliber. Most Spanish Mausers were chambered in 7X57.
Usually the sn and caliber
Old
"anciano" in Spanish means "elderly" or "old person".
Cuantos anos
old lady
Old
old
It's an old-fashioned way of saying: Vi (I saw). From Latin "vidi"> old-fashioned in old Spanish "vide" > modern Spanish "vi"
Although many references have been published on Mauser rifles, I don't know of any that have a complete sn listing.
Antigua
very old
There is no Spanish word spelled "viego". However there is a word only one letter off "Viejo" in Spanish means old, or old man.