Why someone would destroy the crest and place that stamp there is anyone's guess. What is left of the crest looks like the top of the 1891 Argentine Mauser crest, which makes no sense given the 1891 was chambered in the 7.65 x53 round . I don't know where that photo came from but the rifle is definitely the product of a real clown.
The Argentine national crest was ground off by the Argentine government before export. The Argentines had a law requiring the removal of national markings from arms before they could be sold. Almost any example of a model 91 you can find will have been put to the grinder. I've never seen one that hasn't been scalped.
BTW, the Gun Control Act of 1968 requires that any firearm imported into the US has the weapon clearly and permanently marked with the caliber. The caliber stamp on the pictured example may mark it as such a "post-import" rifle. As a rule, those old military rifles didn't have any caliber markings, and didn't need them. The model 38 and 91/38 Carcanos are a rare exception to this, due to WWII breaking out at a very inconvenient time for the Italian army.