Interesting article. The only question I have is this. How would somebody of that era have detected said security measures? Particularly the ink composition?
They were of obviously higher quality material, and counterfeits were typically not too great. Although, the CSA paper money was so poorly printed that counterfeiters often got caught because their bills were better. :^)
A little bit later, every store or shop of any size had a periodical that published pictures of every type of local or state bank currency, hundreds of them. I think that was to help authenticate and spot counterfeits, but it also listed the going rate or discount. A $10 bill from a given bank would not necessarily be spent at par, depending on the perceived soundness of the bank issuing it. It was a real mess, and one reason a central bank was considered an improvement.
not a lot of engravers of excellence around either.