“Massachusetts also designated musket balls legal tender at four per penny [in the 1600s].”
So reports Robert G. Natelson, Paper Money and the Original Understanding of the Coinage Clause, 31 Harv. J. L. & Pub. Pol’y 1017, 1037 (2008), quoting 1 Jerry W. Markham, A Financial History of the United States 46 (2002).