This is an antique, hinged oil lamp shade fitter ring. I think it is somewhat adjustable from about 8"-10". It has a patent date of 1895? ID is 2 1/2".
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.