I work at Boldt Castle in upstate NY, these are on display in the dining room, they are originals from the dining set the owners had in the late 1800s/early 1900s. We've asked a few different historians at various colleges, however, no one has a clue what these were used for. Currently the most believed theory is that they were used to pass small bowls of sugar, or other spread-ables around the table. If anyone can identify what their actual purpose was, that would be awesome!
I don't know but I know that Judith Martin (Miss Manners) writes considerably about flatware and other dining implements so it is possible you can find out in her writings. Or even send a letter if she is still in the business.
/r/whatisthisthing
This is probably a ring in which they used to hold glass teacups. The cups slide in the sleeve and you can then hold the cup with the handle.
Source: no source. I remember my grandmother having something like that.