

But there's a chance that they are the fronts of some kind of European navy buttons. The two thin stamped-sheetbrass buttons with an anchor are front resemble civilian-clothing coat buttons, missing the button's back.

For verification, go to the following website and scroll down to "Examples of Bronze Left-sided Collar Discs, Type 1".

The two discs showing crossed flags, with a screw-pin on the back, are US Army Signal Corps collar-insignia dics, issued from 1910 to 1924. Same emblem but with a raised border/rim and a " BLACK finish" are from the World War One era. The ones showing an eagle underneath a circle of clouds around a group of stars, but without a raised border/rim at the button's edge, are US Army buttons from 1902 to 1910. In case you'd like more-specific IDs of your buttons:
