108.49 is an old gauge number. According to the German 1892 proof tables it stands for a bore or land (NOT groove or bullet!) diameter between 8.89 mm = .350" and 9.14 mm = .360" at the proofhouse. These gauge numbers went out of general use in 1911 (Zella-Mehlis proofhouse)to 1912 (Suhl). So your drilling was most likely made pre-WW1. There should be other regular proofmarks too, eagle, crown/B, crown/U, crown/G. I suspect your drilling is in 9.3x72R instead of 9.3x74R.