Hello Canaan: With a coin in this condition your gentlest cleaning alternative is to take the coin between thumb and fingers and massage it until Social
Security runs out, you develop Carpal Tunnel Syndrome, or you are satisfied (leave at least a
bit of the deposit for contrast). The mild acid and oils secreted by your skin will clean
Roman bronze and alloys and preserve them at the same time. It's why our penny coins tend to last so long, and it won't harm whatever "
silvering" remains. But wash your
hands afterwards. Regards, Jim