Now it doesn't matter what year it is anymore, since I bought it!
My guess/estimate is that it is about 45 years old. Apart from some cracking in the rubstrake and keel guard where it was folded and stored for 40 years it seem fine.
The tubes seem to be a little larger diameter than my -02 Futura and the valves are on another level of course. Nickel plated metal intercommunicating valves instead of those terrible older style plastic recessed valves. The only good thing about the recessed valves is that just, that they are recessed.
The Grand Raid Mk3 seems to give a softer ride than the Futura Mk2c. Less bouncing, but also less speed and G-force in the turns.