This is harder than I thought at first, due to the lack of printing techniques, paper materials, etc. These early notes were printed with caution against counterfeiters, but they were still rife and they are still at it today.
First I bought a book "Early American Paper Money" for under $30.00 from Amazon to read up on them. - Great book. In it it details that there are different types of papers that were used, some with mica flakes, some without, some with hidden text-characters, some without, some intentional misspellings to thwart counterfeiters, some known contemporary counterfeits, etc. Great stuff. Unfortunately, there wasn't enough to get me convinced that I could ascertain on my own without seeing and holding some. So -
I bought these two - my first two - from a reputable dealer trusted worldwide, and who deals with a lot of these notes (Denly's of Boston). Trust in the seller is paramount, especially when learning. I'll have to spend more on issues from other colonies, so I am learning with the cheaper notes.The ones I bought were cheaper notes, and are not encased so I am able to see them, touch them, etc.The inking, can be seen with a loup up close without the plastic, they smell old, feel old, mica flakes shine in the light, etc. Examination on this level has given me a great understanding of the type of papers and printing, This is great, but there are still many varieties out there that are different from the two I have. So -
Buy the book, then the notes - from a trusted dealer. That's how I do it anyway. I really like these notes. The history of early printing, early America, historical times and persons, etc. - So much of it appeals to me. I've wanted to get a representative set for a while. Glad I finally started on it.