You have raised an interesting question regarding the use of German silver, which I'd guess most collectors would like more information on. For a tariff to be put in place, there must have been a prior concern about that item, so German silver must have been coming into the US before the tariff date. I've seen a couple full-stocked rifles in original percussion with German silver inlays that appear to date to the late 1830s from Ohio and Indiana, but they could also have been a few years later.
The brass screws intrigue me. I have not seen what I think are original brass screws on a pre-1842 longrifle...maybe on a REALLY late gun. I think the metal might have been too soft and prone to twist off when used on very hard wood...so I wonder if the tariff was concerned about them being used on something other than guns in 1842??? Shelby Gallien