All turkish Model 1893, 1903 and 1905 Mausers were originally built in 7.65x53. The Turks received a bunch of Gew 98's from the Germans in WW I, and these were all either built as 7.92x57S, or the very early ones would have been converted to S bore by the Germans. In the great Turk rebuild programs of the 1930's, the M1893's, 1903's, 1905's were converted to 7.92x57S, the J bore being LONG obsolete by that time. The Gew's were altered to take the Turkish handguard by boring a rabbet in the front of the receiver and shortening the barrel tennon by two threads to match. These are commonly referred to as "M1938", along with the converted M1903 and 1893 models.
The Turks also received a number of M1888 Commision rifles from the Germans. Many of these were converted by the Germans to load with strippers instead of chargers, and to take the S bore cortridge; but not all were so-modified. I have never owned or examined a Turked M1888, so I can't offer an experienced opinion as to whether the Turked ones were converted to S bore or not. But you can be 99.9% certain that any 7.92 mm Turk Mauser with an 1893, 1903, 1905, or German 1898 action is arranged to fire the S bore cartridge.
Resp'y,
Bob S.
