This one is a bit of a head-scratcher. It's a Scott #71, 30-cent Ben Franklin, used illegally as a revenue on a receipt for purchase of $100 of stamps from the Wheeling, West Virginia post office, signed by the postmaster.
The problem is that there would have been no reason to pay 30 cents tax on this transaction. The ink color and hand of the stamp's cancel match that of the document, so it does not appear that this is a fabrication. Given that the size and color of the stamp match that of the 2-cent Bank Check and the 2-cent USIR, I speculate that the postmaster was in a hurry and grabbed the nearest small orange stamp, thinking it was the appropriate revenue stamp. We'll never know for certain.
Additionally, the stamp is an EFO with an extra row of perforations.