843 So there was watermarks! (twitter.com) posted 3 years ago by Dson 3 years ago by Dson +843 / -0 284 comments share 284 comments share save hide report block hide replies
Whatever they used, it would not be surprising if it was a tightly held secret.
Not like the treasury runs around telling everyone what they put it in money. Kind of defeats the purpose of counterfeit protection.