I should go back and edit my earlier post. It's been a while since I did any research on this. Most of it available on the CR list archives.

Tubing was listed in the catalog as "Record" tubing (you can see that on the Bulgier site), but from what I've read on the archives it was KL. There is no KX. I don't know where I remembered that...old age is creeping up on me I guess.

Aside from weighing the bare frame and comparing it to a Super of identical frame size, or having provenance, it would be hard to distinguish a Mexico from a Super.