The 1891 mauser is a small ring mauser.

If your looking for a sporterized stock for the 1891 Argentine. This looks like the place to get one.

I will be ordering one from them also. I was given a 1891 Argentine mauser that is missing the stock. And I have had no luck finding a military reproduction stock.

http://www.rifle-stocks.com/sporter_hunting_styles.htm