Before the invention of the automatic and quartz movements, pocket watches required being manually wound up, first with the aid of a small key and later, by twisting the crown.
These small and often highly ornate keys were crafted in both gold & silver with a shaft made from steel. Because the pins in the movement were made from steel, gold and silver were far to soft & malleable for the job.
Gentlemen would proudly wear these decorative keys as an attractive & functional addition to their watch chains. Today, the watch key has become the province of ladies, being worn as striking pendants or charms, often suspended as it would have been over a century ago, from an antique Albert chain worn around the neck.