Raimey, as this rifle still is marked with the gauge number 62.78 (,. and / were used interchangeably), it was certainly proofed in Suhl before 1912. The changeover of proofmarkings never was so uniform from proofhouse to proofhouse as the current literature makes us believe. The gauge number 62.78 stand for a bore, not groove or bullet, diameter at the proofhouse between 10.67mm and 10.92mm = gauge # 58.50. The final changeover of the Suhl proofhouse from gauge numbers to tenths of millimeters in 1912 is one of the few rather reliable dates we have. So there is no need to speculate about the gun sitting in a S&S shelf for a long time after 1904, if Stephen's dating is correct.
One should never look at a single obscure stamp and then draw wild conclusions as to maker(s), dating or previous owners.