Out in the woods detecting the other day while down on my knees recovering round balls I saw one of these glass marbles poking out of the dirt. Ended up with four of them. 18th century site. Scored a KG ll coin too.
those marbles appear to be silver fumed or have some other type of luster? Might help you get a pretty close date on them cant remember when that stuff was used
The marbles remind of the ones I've seen used as decoration in a bowl, usually in a bathroom for some strange reason.... Someone might have used them as slingshot ammo... (they make a pretty satisfying POP when they hit something solid)