During the War of Independence, the American colonies printed their own paper currency called the "continental" to finance the war effort. As it happens, the British printed their own unauthorized continentals during this time as well (in New York, for example, which was controlled by the British for most of the war) and readily used them in trade with the Americans. Interestingly, the British continentals were of higher quality (better paper, higher quality engraving) and probably helped fuel some economic activity in the colonies. In a time of war, why would the British want to do this?