I went ahead and bought the Gew 98 this morning and I'm glad I did. The only evidence of "Turk activity" was the stock looked to be lightly sanded, a replacement unserialed Oberndorf bolt (head-spaces fine)/floor-plate, and a rear sling swivel added into the Mauser marked stud. The only Turk marking is the crescent moon property mark.
Stock/HG, TG, action screws, bands, BP, Lange sight, barreled receiver all match.
Come to find out Oberndorf supplied nearly their entire 1918 production to Turkey. Most were converted to the 1938 pattern during refurbs but this one survived. It likely received it's bolt/light sanding in the early 1920s.
I took some DA and a cloth to the years of crud and was surprised to find the stock/HG is very solid with no cracks. The receiver is still in the white but now has a bit of a brown patina.
The bore is excellent, sharp and shiney.....That was a pleasant surprise.