Some of you may be aware that Franklin had one of the earliest liquidity preference theories of interest (maybe the earliest - I'd have to read a lot more of the mercantilists before I claimed that*).
It turns out he also beat Gesell to a stamped money sort of idea too. See Miles Kimball for details.
* - This seems to be one contention of a book I picked up recently by the well known historian of economic thought, Marian Bowley, titled "Studies in the History of Economic Theory Before 1870". It's a relatively innocuous title, and she does cover several issues, but it looks like a lot of time is spent revisiting mercantilist thinking on the interest rate, particularly interest as a monetary phenomenon. Keynes of course credited the mercantilists with a great deal of forward-thinking too, and in the readings I've done in Mun and Malynes I tend to agree.