Another well circulated Currency of Imperial Spain, was The Maravedi. First minted in the 12th Century, it carried onward to the 19th Century. Originally minted in Silver first, these coins were crudely hand minted from silver slag. Although these examples featured excellent relief images, the overall shape was irregular and inconsistent. An average Maravedi consisted of 2.91 grams of Silver. The Gold versions of the coin were commenced in the late 16th Century and were by this time "screw minted" (hand machined). Of a superior quality and shape, they become a dominate coinage in most of Spain's Colonies. Gold Maravedi's were rated at 3.37 grams Gold. The Maravedi was also the lowest form of Spanish Currency used.