Athenian coins, however, were struck on the "Attic" standard, with a drachm equaling of silver. Over time, Athens' plentiful supply of silver from the mines at Laurion and its increasing dominance in trade made this the pre-eminent standard. These coins, known as "owls" because of their central design feature, were also minted to an extremely tight standard of purity and weight. This contributed to their success as the premier trade coin of their era. Tetradrachms on this weight standard continued to be a widely used coin (often the most widely used) through the classical period. By the time of Alexander the Great and his Hellenistic successors, this large denomination was being regularly used to make large payments, or was often saved for hoarding.