Raimey,
Several times, now, prior to posting my question on this site, I looked at the stampings on this rifle, and, frankly, am still somewhat unsure about the proof load powder charge stamping, because, believe it or not, the second digit, on both barrels, is not clear at all. It looks as if the stamp slipped as it was stamped, or the original digit was stamped over again. So, again, it looks to me to be 2,579, but, person who looked at it with me at the same time, took it to be 2,479. To me, it looks to be a 5, much more than it looks to be a 6, but I wouldn't rule out that it could possibly be a 6 too! The bore is much clearer, and easy to see, as 172/28. For certain, the rifle is chambered for the 8x57IR (Americanized, interpreted as 8x57JR), for .318 dia. bullet, as I measured it. The proof stamping changed after 1912, so I am certain that the rifle was made during or prior to 1912, and patents as used on rifle were applied for in 1906, but not granted until 1909, so I thought that a window of when it was made was likely 1909--1912; for sure not prior to 1906, as patents had not been applied for yet. Thank you so much for the additional information; how interesting! I will print that, and keep it with my reference data for German cartridges/German double rifles. Best, Jack