Broadstruck is correct - it's "acid treated", or chemically treated, to be more general.......
It's not an error .....
Retired Collector & Dealer in Major Mint Error Coins & Currency since the 1960's.Co-Author of Whitman's "100 Greatest U.S. Mint Error Coins", and the Error Coin Encyclopedia, Vols., III & IV. Retired Authenticator for Major Mint Errors for PCGS. A 50+ Year PNG Member.A full-time numismatist since 1972, retired in 2022.
Comments
it's "acid treated", or
chemically treated, to
be more general.......
It's not an error .....