The Currency Act of 1764 (4 Geo. III c. 34) extended the 1751 Act to all of the British colonies of North America. Unlike the earlier Act, this statute did not prohibit the colonies from issuing paper money, but it did forbid them from designating future currency emissions as legal tender for public or private debts. This tight money policy created financial difficulties in the colonies, where gold and silver were in short supply. Benjamin Franklin, a colonial agent in London, lobbied for repeal of the Act over the next several years, as did other agents.
The colonial government of the Province of New York insisted that the Currency Act prevented it from providing funds for British troops in compliance with the Quartering Act. As a result, in 1770, Parliament gave permission (10 Geo. Ill c. 35) for New York to issue £120,000 in paper currency for public but not private debts. Parliament extended these concessions to the other colonies in 1773 by amending the Currency Act of 1764 (13 Geo. III c. 57), permitting the colonies to issue paper currency as legal tender for public debts.
Sources: http://en.wikipedia.org/wiki/Currency_Act