Recent post to my paper money blog: https://collectiblemoney.blogspot.com/2020/09/interesting-serial-numbers.html
You can add Flipper Serial Numbers 66996699 turn the bill upside down and it will read 99669966 Here is an example from my collection
Whay denomination? What year? What condition is it in? All these things are factors in determining value. And with Flipper notes it is usually worth what a collector of such cool but not fancy serial numbers is willing to pay for it. But don't expect for it to be a high premium.
