LETTERS

Toning Can Occur, Even in Sealed Coin Holders

In reply to a question in “Coin Clinic,” Mr. Giedroyc didn’t answer the question posed to him but also gave misleading and uninformed information – more of an advertisement for PCGS than anything.

If he was informed about testing of toning of coins while in slabs, PCGS or any other for that matter, he would know that the slabs are not airtight and that in as little as 24 hours silver and copper coins can turn color. (See July 8, 1996, Page 79.) This experiment as oversaw by, (2012, Page 23) give startling details about toning changes from the three grading services.