Mauser made a limited number (~15,000) of 13MM anti-tank weapons based on the 98 in 1918. Does anyone local have an example of these or know who might?
Doubt it, they are very rare. However a guy I used to work with from Venezuala has one in Venezuala with a couple of cases of ammo. His family is very wealthy btw and one of his parents is from Germany. He told me stories of shooting Capivara with it.
When he told me about it, I thought he had a custom mauser in a large caliber and I showed him a 98k I had. He stated that what he had that the bolt was about 3 times as big and upon showing him pictures of 3006, 50 cal, and 20mm, said that it was about the size of the 50 cal.
I know the Finn's had a 20mm Lahti anti-tank weapon during the Winter War. If you are thinking of a different weapon based more directly on the Mauser, do you know when it was introduced?
I saw one at a gun show down in West Palm Beach, Florida a couple of decades ago. It was lying on the table diagonally, corner to corner, and overhung on both ends. Dang that was a big gun!
The strange thing is, I went to high school down there in the early 70's with a kid that claimed his Dad had one, but I was never permitted to see it so I always figured he was just BSing me. I wonder if he was really telling the truth.