Hi, Michele:  You found a musical keychain made by the Reuge company
of Ste Croix, Switzerland.  They made these for some time, during the
1970's through 1990's, I believe.  They do not appear in the current
Reuge catalog.  The gold color is brass, not gold (sorry).

Several tunes were available on the small cylinder movement, so unless
one were to hear the tune it would be hard to say which one you have.

Some folks have removed the musical box from the keychain and put it
on a necklace (my wife, for one).

Regards,

Bill Wineburgh
http://members.aol.com/mboxmuseum/museum.html