So I also have an 1891 Argentine Mauser and from those photos it looks like your stock has been shaved down in the front. Even when original they don't bring more than $300-400. If the crest on the top of your receiver has been ground, the rifle likely saw action in the Chaco War.
My dad purchased my rifle from Sears in 1961. I'll have to ask him if he remembers how much they paid for it. Probably not more than $5-10. I just recently found some old surplus 7.65mm Argentine Ammo for it, can't wait to go shooting
