Since the rifle barrel is clearly gauge marked 118/35 (for a 9,3mm of some sort), yet the rifle muzzle measures in the 8mm range, the barrel has been altered one way or another, most likely by sleeving. The only way to tell what it may be chambered for now is to make a chamber cast, a fairly simple job using "Cerrosafe" available from Brownell's, Midway &etc.
An original barrel in one of the 8mm cartridges of the period this nice Treff was built would be marked 172/28.
And while this one may or may not be chambered for the 8x57R/360, John Stransky's excellent article from Handloader Magazine is shown
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Nice looking drilling, congrats!
