Can't help with the markings, sorry. My references describe the 1904 rifle, and point out how it has several differences from the standard Mausers, and how in the 1930s some were converted to 7.92mm (8mm Mauser)
That might be what you have.
Hope this helps
any decent gunsmith will be able to measure the bore and do a chamber cast to see exactly what it is. Would be smart to have the headspace checked, once its determined what it should be.