Before I saw the size, I was wondering if they might be used as marker pegs. eg. in a cribbage board. They're a bit big for that, but they still might have been used that way.
At Mdina (I know it's a completely different time frame and location) they made stoppers for bottles that were not designed to fit the necks of bottles properly in the first place and they were sold seperately to the bottles. They just sat on top, purely decorative, with no seal being created whatsoever.