Them having a mix of both colors -- on the same side of the same coin no less -- is what seems unusual to me. The one on the upper right has a bit of brass coloring among the bronze, for example. The ones I saw online did not have mixes of both colors.
I don't think they've been cleaned (though I could easily be wrong on this) because when I look at them very closely the luster doesn't change across the coin. Simply being discoloration seems like a reasonable explanation -- I can't say that I've seen a lot of brass coins.
I don't think they've been cleaned (though I could easily be wrong on this) because when I look at them very closely the luster doesn't change across the coin. Simply being discoloration seems like a reasonable explanation -- I can't say that I've seen a lot of brass coins.




















