Technical Whatizzit? From my Banjo?

I'm finally finishing the reassemble on my banjo and look what I find in the box associated with my banjo stuff. A large snap ring! I took the banjo apart last year and don't remember this piece.
Anybody recognize it?

 

Goes in the end to hold the roller bearing place...shud be one for each end.

 

Yep, technically it goes in the brake drum.

 

Right...could have been more clear about that...my bad.

 

Yup! I figured it out just a moment ago while showing it to a buddy. What a relief, I just set the preload on the pinion bearings and was holding off putting the cover etc on it in case I had to take the thing all back apart.
Now, why do I have only one of the damn things?
Ever notice the solution to a problem just gives rise to the new problem? HotRods, go figure.

 

It's the big snap ring that fits in the groove in each rear axle hub.
Be sure to grind angles inward for easy removal.