It has a very interesting notaphilly mark on it stamped twice from flora Indiana my grandfather was a postman before ww2 and after ww2 and how rare are these.
Notaphily - the study of currency and banknotes. Philately - the study of stamps. This probably belongs in the general discussion forum, since it has no applicability to currency.
Physics fan meant that this item seems to not have any relation to paper currency, so you need to find a philatelic forum probably