The bottom line on the receiver ring is the year of manufacture. Thus, your rifle was made in 1902, or 1912, or 1922, etc.
Since you have fired it already, how do the fired cases look? No case head separations? Normal looking primers? No notable case head expansion?
It's a good rifle. My first rifle was an M1916 Oviedo short rifle, and I killed my first deer with it. It may not have the refinements of newer mauser designs, but in it's original caliber, served it's purpose well. As far as handloading for it, stick to factory loads or equivalents for safety. Rebarreling options are rather limited to the original caliber, or maybe 6.5x55. It is NOT suitable or safe to consider rebarrelling to newer, higher pressure calibers.