An interesting thread is developing on the Gunboards Forum. On the "Military Mauser Forum", a Poster started a thread - "1891 argentine in 30-40 Krag!".

The Poster had seen an early Mauser in a gun shop that he took to be an 1891 Argentine Mauser. It was marked 30-40 on the barrel. The rifle had few if any markings, no crest, and no graduations on the rear sight.

He asked about it on the Mauser forum. He went back to the gun shop to take some pictures and get more information.

The shop owner asked him what he was doing? The poster asked if the rifle was for sale and got it for $300.

The two pictures, he posted so far, are intriguing!

It appears he may have obtained a rifle that was submitted for the 1892 U.S. Trials (Mauser entry #4 in an experimental .30 cal. rimmed cartridge). (The 30-40 marking may have been added later).

Hopefully, more pictures will be posted. Definitely worth looking at!

p.s. It appears like trial rifle No. 27, (Mauser entry #4), illustrated in Brophy, The Krag Rifle, page 245.