I have attached a better picture of the date marking if this is what it is. It definitely shows 8/24.
I will do a chamber cast to just confirm the caliber but JTPlumb would the 8x57 be followed by a J ?

[Linked Image from jpgbox.com]

Do any of the marks indicate who the builder was? If I understand correctly a builder in Shul would build the Drilling and then the Distributer would send it to be finished, engraving etc.

I have a solid red pad I plan on having installed this week, then test fire. Barrels are excellent. Prior to the long term storage someone had cleaned the bores and then placed oiled patches in the barrels. Kind of a pain to get out but it seems to have worked.