The auction was from June 30 2012, I only saved the pictures. I have a few more but they are not great pictures. I will post them all. While the bridge hole pattern is different than the MO/17 Turks it seems, it is consistent with another Danzig/17 bridge, which has 5 holes in the rear base.
It is only my speculation as to the origins of the rifle, you might wait for Wolfgang to show up here, he usually does between his busy schedule, or take it to the sniper forum, he goes there too and some other sniper rifle collectors go there also and they might be able to illuminate the topic for you. There are several threads on Turkish snipers; so far all are MO/1917 in the "n" block, though it is well known Turkey received rifles from other manufacturers also. While MO is recognized as the primary supplier, through Spandau, rifles made by other firms often show up with signs of Turkish use.
Further, these sniper rifles are speculated issued to the German soldiers that served in Turkey, several units did, and then at the end of the war the Germans left them behind, which is probably what happened. But, some think they were issued to Turkish units also. Which isn't impossible of course, the Germans did supply the Turks with all means possible to contribute to tying down Entente forces in this backwater theater.
Personally, I think it isn't likely many were issued to Turkish troops, perhaps some specially trained men, but while the average Turkish soldier was a good fighter, when well led, they were not exactly the best candidates for precision equipment. At least without suitable selection and training, - obviously if Russians in World War II could be found in number to become snipers, Turks could as well, it would just require suitable selection and training of men. Which requires time, - which was limited by the time a supply line was established and the time the Turks surrendered.
Anyway, the rifle has some characteristics of the Turkish service rifles, including the bridge pattern and prefix; I think it is worth pursuing the possibility with those that are more familiar with sniper rifles.