I’ve done a bit of Googling concerning 1930’s Ratier propellers, and it seems that the situation may be a bit more complex than I assumed. Ratier were amongst the first companies to produce a commercially-successful vairable-pitch propeller, and the pace of development during that early period was quite rapid. Ratier (still in the propeller business, as Ratier-Figeac) has an interesting web page on their development history (in French, but Google translate seems to work well enough).
http://www.ratier.org/helmet_.html
Given the time period, it seems possible that the C.430 could have been fitted with either a mechanically-operated variable-pitch propeller, or possibly with their pneumatically-operated automatic two-position propeller. The latter was an interesting concept in that it was set at fine pitch on the ground, and used an air bladder (previously inflated by a gonfleur d’hélice with a bicycle pump!) to move it to coarse pitch after takeoff - with increasing force on a metal disk mounted on the front being used as the trigger for the pitch transition. Looking at the picture of Helene Boucher’s Rafale from Wikipedia, there does appear to be a disk of some sort on the front of the propeller hub.
Modelling the C.430 with the pneumatic type, if that is what it actually had, would probably be rather tricky though, and might be rather confusing for most simmers. It was entirely automatic, and had no mechanism to return it to fine pitch in the air, which could be hazardous in a go-around situation. I think most people would be happy enough to accept the existing modelling as it is, even if it isn’t entirely correct. Maybe BlueMesh3192 knows more though, and can tell us which type is being modelled. If it is the pneumatic version, that would explain the apparent lack of any pitch control mechanism in the cockpit.