Anybody know what this nub is for?

[AndyA]

Dear vintage lightweight gurus:
There is a nub on the inside of the right seat stay of my vintage Lotus Excell 12-speed. It's about 6 inches up from the dropout. Looks like it might be useful for something, but what? This prompts another question: Do I have too much time on my hands?
Thank you for your support.

 

[fattyre]

To hold the chain while the rear wheel is off the bike.

 

[AndyA]

Professor Fattyre:
You are my hero! Next time I have the wheel off, I'll have to try it out. However, it does seem a bit like a solution looking for a problem.
Thanks!

 

[Mr. Monkeyarms]

Makes wheel change a breeze!