Argentina was one of the first countries to adopt Mauser rifles, with the Model 1891. These were replaced by newer Model 1909 rifles a couple decades later, and in 1913 they bought 500 telescopic sights to make sniper rifles. All of them appear to have been put on cavalry carbines like this one, rather than full-length infantry rifles. The scopes were 3x fixed power types made by SOM in France. The mounting system was either developed by the French or later copied by the French, as it is very similar to the late-war WW1 pattern of scope mount used by the French Army on the Lebel (and the Argentine scopes are very similar to the APX 1916 French scopes).

This is a quite rare complete matching rig, with the rifle, mounts, scope, and scope case.