The M48 was indeed a military rifle produced in Yugoslavia in the late 1940s and early 1950s. It's a bolt action rifle chambered in 7.92x57mm. It's supposedly pretty fun to shoot, and ammunition is plentiful and dirt cheap.
We have a special forum for guns like that here at ARFCOM, it's called the
Curio & Relic forum. Make a post about it in there; they'll tell you everything you need to know.
If you want to get some more information and read some articles on it, you can head on over to
www.surplusrifle.com. It's a whole website that is dedicated to older military rifles such as the M48.
Here is their page for the M48; you can see a big ol' list of M48-related articles on the right side of the page.
Hope this helped.
ETA: Yes, 7.92x57 and 8mm Mauser are the same thing, just different names.