The caseback and thus the case are GP. I can not see the movement in sufficient clarity to examine any markings. It should be marked with a script font Girard Perregaux 17 jewels and probably unadjusted. You can check Dr. Ranfft's movement archive for a matching movement (google will direct you). Ranfft will also give you an idea on the dating.
The dial is probably refinished given the interior case discolorization... the dial would have suffered something similar... and its fairly pristine appearance.
If the movement is real, it is probably real with a caveat on who knows what the original dial looked like...
A forum community dedicated to watch owners and enthusiasts. Come join the discussion about watch collections, displays, watch winders, accessories, classifieds, and more! We welcome all manufacturers including Casio G-Shock, OMEGA, Rolex, Breitling, Rolex and Tudor, Seiko, Grand Seiko and others.