I am still trying to understand Shimano model numbers - I have a Shimano DuraAce AX seat pin - where does this fall into their range?
Dura Ace was the top group, but came in two variants: AX and EX. EX had more traditional styling (with 7200 serial numbers), while AX was the more modern aerodynamic variant (7300). It's probably simplest to direct you to the 1982 catalogue here:
Your AX seatpost will be one of the variants shown here (7300 series):
Similarly, 600 (one down from the top) came in AX and EX variants.
Calmes dans le demi-jour
Que les branches hautes font,
Pénétrons bien notre amour
De ce silence profond.