Came to inherit this part but no real idea what or who makes it?
Looks like some sort of headset thing, pictures to follow when I find out how
Left-handed high flanged BSA full compliment external bearing race?
Looks like a headset reducer thing. Or some frames back in the day had removable head tube inserts to allow you to switch between 1.125" and 1.5" (think Scott did for a while maybe).
Might be from a Scott Octane like this (you can see the headtube is kinda held in place by "mesh"): (4) Scott high octane frame help. | Retrobike
It's definately for a headset, but no idea what bike. internal ID is for 1-1/8", external it measures pretty much 56mm OD
It's also 56mm across the flats so looks very much like a scott octane headset thing. Thanks STW collective!
The +1 degree and - 1 degree markings on it suggest angle adjust headtube insert. The Scott Gambler DH frame fro. Around 2010, 2011 ish used one just like it.
The Ritchie brandedpartswillbe the actual headset inserts pressed into it.