coin if it has been drenched in e coli bacteria. Circulated coins and used stamps can be covered in boiling water and are harmless and good to go. My bucket list caused me to complete all of my collections at the same time from my 401k funds after they became penalty free to withdraw. Within a year my wife's medical problems had me shopping those key date problem free coins. That was an education. I already knew what a bath I would take on common coins. I foolishly assumed that key dates would be easier to sell and bring more of a percentage of book value.