Pics would be most beneficial especially of the area between the flats and the forend lug down around the lower ribe where the mechanic's initials can be found.

Even though the firearms merchant has an address in Hamburg, the dreiling was made in Zella Mehlis(lower probability for Suhl). Zella Mehlis required the date stamp October 1st, 1911 while Suhl began September 1923. But Zella-Mehlis was dating some examples a good 10 years prior.

172.28 is the pre-rifled bore diameter measured with the plug gauge 172.28, which would pass the whole length while the next plug gauge in line would not. This designation only gives the diameter and was used up to 1910, when it was replaced by the "mm" stamp, but there are exceptions to the rule like yours. I'm not sure about the "58" and it might indicate length but that's a wild guess and may narrow the field to the 8x58R Collath or 8x58R Sauer and that would be interesting. I'd guess the cartridge to be the 8x57R/360, which also is in the 9.3mm family based on the British 360" BPE. A cast will provide the answers.

Since the "7.11" has the decimal, it would have passed the proofhouse, more than likely Zella-Mehlis, in July 1911. Just think next year this time it will be 100 years old. The "511" below notes it was the 5 hundred 11th example to pass thru in July of 1911. The encircled "16" on the scattergun tubes notes bore number, 65mm chambers and black powder while the vulgar fraction next to it notes the diameter at the muzzle unless the tube has greater than .008" constriction and then the value is the diameter at 22cm ahead of the standing breech. "Crown" over "W" denotes choke as well as an additional proof effort.

The "Crown" over "N" 1,8g GBP over St m g is an early volunteer smokeless proof noting the use of Gewehr Bläattchenpulver, military flake powder, and a steel jacket bullet. This may point to the cartridge being a relative of the 8x57IR.

Is it a hammer or hammerless and with the Krupp tubes it may have been sourced from Sauer and be one of their production models.

Kind Regards,

Raimey
rse