Reddit reviews Mauser Military Rifles of the World

Manufactured in 1943, it's an 1898 derivative of some sort?

My dad's got a Mauser 1893 (manufactured in 1896, with the Spanish coat of arms) that got bubba'd, though not nearly as bad as yours. Replaced the original stock outright (a rather nice one, but not the original), replaced the sights, cut down the barrel, and turned down the bolt. I've thought about converting it to a proper carbine (some of the modification done by bubba were done at the factory for the carbines), as well as rechambering to something less expensive to shoot (7x57mm is at least $0.80/round, and not easy to find). If you go this way, there's a book on Mauser military rifles (fairly certain this is it, I got it from the public library). In your case, since the receiver has already been drilled, you might consider finding a stock and scope, and turning it into a sniper lookalike; if you can't use the existing holes, the scope will at least help to hide them. You might also try your hand at making a stock yourself, if you have any interest in woodworking; either a nice sporterized one, or a replica of the original.