... not to mention rare.
Documents from the U.S. Civil War era that feature both U.S. revenue stamps and revenue stamps/imprints from other countries are quite scarce, and depending on the countries in question, outright rare.
I stumbled across this document on eBay
where it had sat for over 3 months, in a category revenue collectors wouldn't have normally looked, being sold by a seller in Spain, with no reference in the title about there being U.S. revenue stamps affixed.
It is beat to heck and back, and just taking it out of its holder to try and scan it gave me heart palpitations; given the (effectively) tissue paper it's printed on, I'm surprised it still exists.
It's a sister (sequentially numbered in fact) to one featured by Mike Mahler in his incredible current 40-page exhibit "Once Was Not Enough: Multiple Taxation on Documents of the U.S. Civil War Tax Era, 1862–1883", and the specifics about the transaction and rates come from him:
An 1863 first bill of exchange, Havana Cuba, drawn on a party in New York, in the amount of $1,400. Taxed 14 cents (short-lived Inland Exchange 1863 rate of 2c per $200), with Cuba 1 escudo Giro ('Draft') tax paid in 1868 to ensure legality in a long-running legal action.