Why did ancient kings start stamping their own faces onto metal?

A ruler's mark worked as a guarantee. Before coins, people paid with lumps of precious metal valued by weight, called bullion. Every deal meant weighing the metal and checking its purity. A ruler's stamp promised in advance that this was already done. Historians think stamping busts and designs probably began this way, though showing off a ruler's glory may also have played a part.

Yet the very first coins showed no face at all. They appeared in the kingdom of Lydia, in what's now western Turkey, in the late 7th century BC. King Alyattes had his stamped with a lion's head, his dynasty's symbol. They were made of electrum, a natural mix of gold and silver. Its gold content varied wildly, so even a stamped coin's true value stayed uncertain.

His son Croesus fixed that. Lydia's gold was purified by heating it with salt to remove the silver. Croesus is credited with the first true gold coins of standardized purity, made for everyday use. Buyers no longer had to test the metal: the stamp did it for them.

Real faces came later. The first portraits of actual rulers appeared on coins from Lycia, in the 5th century BC. From Alexander the Great onward, the ruler's portrait became standard. The stamp also invited a new trick: clipping slivers of metal off the edge, then spending the lighter coin as if nothing was missing.