Re: very short mauser ID.
The rifle was produced in quantity by FN circa 1947 in 7X57, .30-06, 7.65 and 8X57. Some were later converted to .308. The original specified factory barrel length was 17 1/2 inches The rifles were sold in seeming 5,000 unit contract quantities to police departments in Mexico, Columbia, Uruguay, Holland and others. I have only seen three repatriated rifles over the years and those were in the .30-06 chambering. Yours could possibly be in any of the other calibers. Cast the chamber if in doubt. I once owned a mixed pieces parts .30-06 version that shot quite well, but it was also a pretty decent shoulder thumper as you might expect.