That is a Gewehr 88/05. Made in 1891 at Spandau. Sometime around 1905-1910ish it would have been updated to use the new 'Patrone S' spitzer round. The modifications included modifying the receiver and magazine to hold cartridges without a mannlicher clip, modifying the receiver to accept the new stripper clips, modifying the receiver with the divot to allow loading from stripper clips (the overall length of the cartridge never changed, it was do with the stripper clip loading), and re-calibrating the sights for the new round.
These rifles were then used in WWI by the Germans, as a secondary arm which still saw a lot of frontline service. As the war progressed the need to use the 88/05s started to dry up (as they now had enough Gewehr 98s) and they ended up being stockpiled. In 1916 they started sending them to the Ottoman Empire, who used them up into the 1920s or 30s (including all the conflicts fought by Turkey in the 20s) before putting them into storage after a rebuild. Part of them being sent to the Ottomans was to have the rear sight markings ground down and put on in Arabic numerals. Ironically the Turks later on in rebuild would often grind off the Arabic numerals and replace them with standard numerals, I have a example of a 88/05 with that exact treatment.
Things to note, your bore is very likely not .323, but rather a .3215 diameter bore. Unless you have slugged it and 100% confirmed it is a .323 bore I would not shoot any .323 bullets out of it. These are weak actions and have been known to blow up in both German and Turkish service. That being said these rifles are a blast to shoot if you get set up for reloading. I personally use .32 Winchester Special bullets (.321 dia) and some 3031 powder (can't remember the exact amount off the top of my head), and it is one of my most accurate milsurps. You need to load light, but that also means there is next to no kick when shooting them.