At first I thought it was a coin holder, making a pendant type necklace.
As CP wondered, what is the thickness and diameter?
Locket: Solid stem, no hole through to inside of case.
Spring on the outside under the stem, if that is the remains of a spring under the stem.
If smaller than say, a quarter.
Very thin.
If it's made of brass.
Watch frame: Hollow stem for the winding and setting stem. Even most key wound watches had a stem for setting.
Relatively thick.
If it's made of steel, silver or gold.
Both would have a cover and opened when the stem was pressed to release the catch visible under the stem on the rim. Both would have a ring attached at the little knobs on the side of the stem.
I think the defining factor would be the stem, if it's solid with no hole through to the inside of the case, it's probably a locket.
The first picture looks like the stem is hollow, so then it's probably a watch.
Most watches had internal springs for the catch, many lockets had external springs. But some lockets had internal springs.
But I have a gold locket and a brass watch. I never saw a coin holder with a cover, but I haven't seen everything!
So, after carefully analyzing all the data, we can safely assume that it's either a locket or watch frame or maybe a coin holder.
Hope this helps.
Musketeer