Antique dating pocket swiss watch
If there is no metal cover over the dial, then it's an "open face" watch.An open-face watch just has a "crystal" over the dial (usually made of mineral glass).
Sometimes the bezel (the round metal ring that retains the crystal) is lost, which makes it impossible to replace the missing glass (see this article for more information on vintage pocket watch bezels).
Note that in the photos above, the winding stem is at the position on the hunter-cased and demi-hunter-cased watches, and in the position on the open-face watch. Movements were made either for a hunter-case or for an open-face case.
The primary difference between a hunter-case movement and an open-face movement is the relative positioning of the winding arbor and the seconds bit, and the positions of the dial-feet.
The movements had various quality designations, usually related to jewelling.
Some were signed with names such as “Romney”, “Greenleaf” or “Craig”.Thus the demi-hunter provided the convenience of an open-face watch with the protection of a hunter-cased watch.