Yes... Otsby & Barton were a jewelry firm out of Providence, Rhode Island... their firm started sometime in the 1870's and were in business until about the 1950's. Damndest thing about them too...turns out the Otsby fellow and his daughter went to Europe in 1912 to research designs and maybe purchase jewels for the business, did quite well actually. The bad decision was on the way home, when they decided to board the Titanic for the trip home. The daughter survived.
The firm continued with the "O B" hallmark, well after Mr. Otsby perished.
This info that I'm posting comes from memory, on the research I did on my own ring, that had the same mark as yours.. so the facts I listed might be a little hazy, but you get the gist of it...
You found a beauty of a ring by the way....Congrats!!!