Not a HG lock ring, way too big. It’d be loose on the cassette body.
Don’t think they’re fork bushings. Made of alu.
BB related? Maaybe but don’t think I’ve had anything too odd. Or anything I don’t know all the bits.
Smaller than 1.5, I _did_ have a giant trance frame and giant were into 1 1/4 for a bit, hmmmm could be related to that.
Or some sort of headset part, can’t think what for though. Maybe each 5mm thick?