Antique?Watch with Red 12 white star outlined in black and RW etched on back

This is an old (antique) watch that I found with some of my grandmothers things. It intrigues me because I don't know how old it is or what type of watch it is. On the face it has a red number 12 and a white star outlined in black, it says Swiss Made on the bottom of the face. On the back it has RW etched into a box of some sort, then the words metal chrome and a number on the side of 3900 (2)? (4)?
If anyone has any information about this watch I would love to know about it!