The Gran Sport seatpost came out with the Gran Sport brakesets, they finished off the Gran Sport or Nuovo Gran Sport ensemble. The only the rear derailuer got the Nuovo typography addition. the earliest G.S. seat posts were essentially Record posts in a green box. Later there was an evolution to a coarser texture above the machined cylinder, and the machining was done faster, so there were more visible machining marks. around '79 some posts had G.S. stamped into them... my guess to help tell the difference. They were only minimally cheaper to buy wholesale individually.
A bit later the Record post got the alloy lower cradle ears and the adjustment bolt barrel nuts were machined at the ends a bit differently.
But beware, things kind of flopped back and forth, stocks of these parts did not get rotated sometimes, so detail changes appear hap hazard.