The signs known as 'masons' marks' were carved on blocks of stone in Bronze Age Crete over a period of some 500 years from around 2000 BC until the middle of the 15th century bc. The earliest examples seem to occur at Knossos, dating from the time when the so-called Early Palace was constructed there. Soon thereafter blocks with comparable signs were incorporated in the palatial centers at Phaistos and Malia. In due course, the practice spread elsewhere...