Parts ID help please

This little part was in one of the boxes of N15CS that I got, and I never have figured out what it is. There were non Norton parts mixed in, so I can't even tell if it is for the bike. Haven't seen in any of the parts diagrams that I've referenced during the rebuild. Any help appreciated.

~Tom

Axel spacer maybe for Girder front end, One of the experts will know, we'll see if I'm close!

Here are pics with measurements and a spark plug next to it for perspective, should have done that first time. Imgur is not allowing me to resize, seems much slower to allow that so these are big too.