Good info from Mike and Raimey. The 172,78 mark that appears on both the drilling and the kiplauf is the "gauge" of the rifle barrel in the same sense that shotguns are 12 or 20 gauge. 172,28 will be an 8mm of some sort which could be any of a dozen different cartridges. Most common in these type rifles is the 8x57JR, others as mentioned above might include the 8x57R/360, 8x58R or 8x48R Sauer, 8,15x46R or even an American round like Raimey says - only a chamber cast can tell you for certain.