This maker likely isn't famous since it's been a real struggle to find them, but the curiosity is eating me alive, so thought I'd see if anyone here knows. Possibly JC but maybe not? Eagle mark is 4, I've found several different names with that mark so I think in that case is a city (maybe Guadalajara, but not 100% on that).
I don't have the books, so maybe someone can find something. I did find a JJC on another site, but unidentified maker.
Thank you for your time!
Wonder