After lots of research I can only guess that this is a totally custom item made for an individual. A winged propeller onlaid onto the gold fill bangle made me originally think it was a WW2 Air Force sweetheart jewel, and that may be true. The Greek letters Phi and Upsilon have me stumped though. Is this for a fraternity? Other honorary organization associated with aviation? 7.5" inner diameter. Opens on an expanding rod.