This is an antique brass fence or chimney fitter ring for an oil lamp. It has a 4" OD and probably fits a 3" chimney. It has a 2" ID. It looks to have been modified slightly on the inside, but should still be functional and probably not noticeable. On the inside it is written Ro. No. 127410.
I purchased a partial estate LOADED with oil and gas lamps, shades, burners, flame spreaders, chimneys, sconces, tanks, and literally thousands of parts, which I will be listing over the next couple weeks so be sure to check out my store and add to favorites.
Liquidation Services buys partial estates, collections, accumulations and also storage units at auction and you really do find anything and everything in them! 95% of items purchased will be listed for sale here.