Robert Ball's Mauser Military Rifles of the World 5th Edition has several pages on Persian Mauser rifles. E-books are available online through legitimate retailers and other file sharing sources.
It's a Spanish M43 rifle made for the Spanish Air Force. The tag is largely incorrect. It was made in Spain and not Germany. It's an 1898 pattern Mauser but it's not a Gew 98. Page 358 in Robert Ball's MMROW has details on it. Hard copies are expensive now that it's out of print, but the ebook is pretty cheap
The price is too high in my opinion.
Mauser Military Rifles of the World https://www.amazon.com/dp/B005I5ELR0/ref=cm_sw_r_cp_api_N7SQDWRGPB82DM5V6HWN
Some of it is outdated or just incorrect, but still a good source.