Dating back to the Victorian times, watch fobs gained popularity as an accessory to the pocket watch. Serving in mainly a decorative role, the fob jazzed up a typical pocket watch by adding a bit of bling and symbol of membership or achievement. The fob hung from the chain that was attached to a jacket or hung from a vest pocket, and many were engraved with initials and dated on the back.
Now many jewelry artists (like me) are using them as the focal piece in creations due to the fascinating history behind each piece.
If you want more information on watch fobs, check out this article on eBay.