Need Help

[Brush4]

Last year i found a copper makup compact about 4" down it had a painted surface on top with a man and a woman riding a two seater bike with a dog chasing them the woman was wearing a dress and the man had a suit with top hat it came out of the ground in perfect condition i gently washed it and set it out to dry the next morning the paint had all flaked off i was sick any help on preserving somthing like that!!