My response... giggling at the notion that 1960's - 1990's are *older* notes. 1761 says "Hi..." Oh and it says collect anything you darn well feel, it's your collection. If *you* like it, then go for it. But collect because it interests you, not because it's valuable to others, because later issues rarely will be.
I take the Bank Note Reporter for current news and for a base of prices. One book to get that is some way up to date is "Standard Guide to Small-Size U. S. Paper money from 1928 to date. Another is "Paper Money of the United States" a complete Illustrated Guide With Valuations by Arthur L, & Ira S. Friedberg 2017.
Not sure of your location but this was done in California years ago. The only way to tell it was a five was the security thread.
In reviewing numerous past CoinTalk e-mails for which I hadn't had time, I opened this thread expecting to see a discussion of Large Size U.S. Currency. A large guffaw escaped my mouth when I saw the actual notes under discussion …obviously "older" is in the mind of the holder. It brought to my mind when I purchased with my father a coin shop in Freeport, Grand Bahama Island, BAHAMAS in 1972. In reviewing the inventory on 31July1972, we split with the vending owner a very limited stock of circulated Bahamian Sterling Denominated currency literally thumb-tacked on the wall. The Bahamas had decimalized scarcely six years earlier on 25May1966. That was the beginning of my deep dive into Bahamian Sterling Currency, of which I may be the world's premier maven, but of which too few really care. My "dive" has involved hundreds of hours in original research, revisions in identification and a few published articles on Bahamian currency. However, the market reality is that I probably would have been further ahead financially if I had intermittently purchased CU groups of newly issued decimal currency. So… who am I to laugh or be skeptical of what someone else calls older???