What does 18K gold mean on a watch?

On a watch, 18K gold means that the watch features genuine gold. An alloy, 18-karat gold is 75% pure gold and 25% other metals. The high gold content gives the metal an attractive color, while the alloy metals add strength to increase its durability. An 18-karat gold watch may be solid gold or gold-filled, which means it is primarily another metal that the watchmaker finished with a thin layer of 18-karat gold. On 1stDibs, find a large selection of gold watches.