Good afternoon, Since I’ve started cataloging my coins, I’ve come across an oily residue on some coins that have been kept in their original plastic/vinyl wallets from the Royal Australian Mint.
It appears as tiny dots similar to pitting on the coin, but can be wiped off. It also seems to be on the inside and outside (to a smaller degree) of the sleeves the coins are kept in (see images). I thought it was age related as the first two sets I found it in were my UNC Year sets from 1970 and 1971, however my 1982 UNC Comm Games $10 Silver Coin has the same.
While I just wiped the coins off with a tissue on the early sets, I’m more relunctant to do that on the $10 as it’s a nice looking coin. I’m sure it’s a well-known thing...I’m just new to the group and would appreciate some advice on what it is and how I deal with it. Thanks folks,