GP is one of very few manaufactures who actually did sell the examples that passed the Observatory Chronometer certification, which was far, far, far, tougher hurdle than today's COSC (daily deviation less than +/- 0.75 sec, etc.), when most other brands submitted with the mentality of F1 racing meaning that the examples they submitted were meant to last only for 45 days and not to be used daily as wristwatches.
Anyway, belatedly, thank you for reminding us of these great models. From design, I like Opera 1, I really would love to see it in person...
Thanks again, FX!
Ken