A pilot I knew who was also a coin collector told me to put the damaged coins in olive oil & store them in the freezer for 6 mos at a time then swirl the coins in the paste-like frozen olive oil for 2 days until the olive oil melted, then repeat the process for as many yrs as it took until the coins started to look close to normal; so after 30 yrs I noticed that some old coins I found in an old leather coin purse in an old desk seemed very well preserved, I figured "what the hell?" & put the best looking coins in the purse for a couple of years. The funny thing is that the best looking dime is totally black but every detail is sharp. You asked about the olive oil & leather purse!
