I think I may have found something that's actually rare.

I have found a Peruvian M91 (Argentine) carbine. DWM manufacture.
I think it qualifies as 'rare', as anything I look up concerning 'Peruvian M91 carbine' comes back as the Argentine M91 rifles sold to Peru in 1901 and were cut down from those for the Peruvian navy. All images I find and all info I can muster shows these 'carbines' with the 'lange vizier' rear sight.
I have not found ONE photo of this type of Peruvian/Argentine M91 carbine..yet here one is. Receiver, barrel, and number on the buttstock match. Bolt does not (par for the course with these, as I understand Peru stored rifles and bolts seperately)
Has anyone at all seen a Peruvian '91 carbine like this?

Yes, I agree that is a rarity. No hint of it in Ball. So until someone comes up with a better solution, I suggest that it is an originally Argentine 1891 carbine that was acquired by Peru, and either had the Argentine-marked system housing replaced by a Peruvian one or had the crest ground off and restamped with the Peruvian crest.

Perhaps a trial made before the Peruvians decide to cut down their 1891 long rifles instead? In which case it might be not just a rarity, but actually unique.

The Lange Vizier sight signifies the barrel was replaced on Peruvian Mausers, it was not how they originally started. This one might have just had a good enough barrel not to be replaced.

Awesome find. looks to be in great condition as well.