Swedish mauser??, help

Cleaning out my grandpa's house after he passed away I found a rifle. I'm pretty sure it's a Swedish mauser, but other than that I'm lost. In front of the bolt it has Carl Gustafs Stads Gevarsfaktori 1903, above that there's a crown w/ a "C". Next to that it says K.B. 133055 (S/N?), 055 is marked on several other places. However, the front and rear sights seem to be in much better shape than the rest of the rifle and don't seem to match. The rifle is 36 3/4 inches and the barrel is 18 3/8 inches from start of breech to end of barrel. Any help in figuring out the exacts of this rifle will be appreciated.
I think it may have been "customized" years ago.