actually I think you'll find those Simplex derailleurs to work better than the Hurets, they just aren't as light or pretty...probably about as good as the Shimano 600 and/or SunTour that they resemble. The weak point is the flimsy plastic wings on the shift levers, but even when they break off you can still use the levers with just the metal bolts. I'd guess about '78 for this one, but now will look for the catalog to confirm/deny that guess.
Well, the catalogs are a little short on info, but looks like this model matches a '78 French-market frame-wise, but not with the Simplex drivetrain, and the US '79 catalog shows a different paint scheme and a Japanese drivetrain...I also thought that RD was more like "1980 and later", so I'm not sure of an exact date, but would still say around '78 to '80
check it out yourself:
http://www.calameo.com/books/000052438aab92476138e
and check Velobase for more catalog scans.