Verdigris. Leitz Summitar 50mm

I noticed this very substantial hook/doorstop which has been holding the teak door of a Harvard building open since the late 19th century.  There's only one way for it to have acquired that verdigris and that's by being made of some cuprous metal alloy - brass or bronze.  Interestingly though, the loop holding the hook where the verdigris is worn away looks like iron, but that doesn't make sense.  At any rate, it's pretty in its greenness and so substantially set into the granite step.  They built things the right way back then.