I recently discovered this interesting site which has vintage guitar catalogues available for a small subscription fee.
Included is a 4-page El Degas Guitar Catalog for 1973.

Looks like a good resource for anyone wanting historical background information on items in their guitar collection.
REVIEWS
Also for those who may not be aware of it, an excellent site called Harmony Central is one of the definitive references for guitar and gear of all kinds. They have a good selection of El Degas reviews available which may help answer some of your questions from a musician's/player's point of view.

LABELS
I found these label pix and thought you might find them interesting.
Korean & Romanian Labels


Compare these to the MIJ label on my GB25 post

Kinda interesting to note that the MIJ labels seem to have an actual Serie No, while the MIK have a space for one but usually don't have anything there. By the time you get to the MIR label they've dropped all pretense at even offering a number!
I guess that was the beginning of the end for the once amazing El Degas line (sigh).