Turkish Mauser. Greywuuf.
Years ago I got stuck with a Turk "93" Mauser looking rifle. Not made by Mauser.
Mine is a long rifle and has a mis matched bolt. [square bottom]. Is marked the same as you state yours is. Has the year stamped 1956. Astonishing to discover that anyone would make such an antiquated gun such as this in 1956. That must be the year it was converted.
This rifle has had some sort of a magazine cut off at some time in it's previous life and now it is non operable.
This gun is chambered in 8mm mauser and I have not fired it in twenty or so years. I suspect it started out as a 7.65 Belgian/Turk. If you live close enough to do face to face transfer I will give you the rifle.
Not worth it to me to go to the trouble to send it anywhere.
Your action will be plenty strong for the .45 auto cartridge.
Life is good