I think you spelled thinger majigger wrong. I think it's supposed to be thinger-majigger Isn't that the end piece on the spring on some older shock absorbers? Kind of like this thinger-majigger.
If it is brass, it may be the "foot" of a chair, which when mated with a concave piece above or below it on the chair leg, allows the leg to always find "level" on the floor. Cool find, Sub