Forgive me if this is a question that has been previously asked or has an incredibly obvious answer but I couldn't find any concrete information through searching.
I've seen a
fair number of
billon tets with this kind of corrosion around the edges and was just curious what actually causes them to become so pockmarked, and in some cases rather 'lumpy' in character.
An example is attached, though perhaps not the best now that I look at it more closely as it doesn't quite show the 'lumpy' characteristic. This particular specimen should be a
Maximianus billon tet. Minted in
Alexandria.
Obv. MAΞIMIANOCCEB, laureate and draped
bust right.
Rev. Nike walking right, holding
palm branch and
wreath. L Z across fields. Γ in
exergue.
Milne 5049.
