I think it can be both Swiss and DWM.
Switzerland apparently bought guns from Germany for a good while before tooling up themselves. I see listings at Simpson Ltd for 1900, 1906, and 1920 DWMs with Swiss shield. The 06/1924 was made in Bern, as was the stripped down 1929 with ugly straight frontstrap.
The "gold colored" parts are known as straw parts, the color coming from heat treatment with no finish applied.
The "hallmarks" are proof marks from the maker and maybe the user.
I do not know the significance of the P51.