This is a wonderful item, IMO. Another example of how searching outside of the normal stamps category on eBay can pay dividends.

It’s Scott # RU4a used improperly as a documentary on an 1869 one-day promissory note, tied by manuscript cancel in the same hand that wrote the note. The manuscript cancel is “TK AP 6 1869”, the unusual month abbreviation matching that used at upper right.

5 cents was the correct tax rate for this transaction.

Mann’s Choice is a tiny borough in western Pennsylvania, population 363 in 1890 (its high point given on Wikipedia, also the earliest year listed), population 311 in 2021.