All Oz GTs would/should have been fitted with the Mk2 S displacers: silver colour-coded. Green displacers were on late DeLuxe and K.
Yellow was an early slightly stiffer displacer used in mid-'60s on Ss before blue, then silver. Obviously, people fitted replacement bits from wherever they could find them.

Is the green identifier one shorter than the orange? The Mk 1 Cooper S & Deluxe were introduced with a shorter strut (red dot painted on strut) and an accompanying lengthened helper spring [21A 1806] at car # 16758 & #1221 respectively. No further record changes I can determine thereafter, so would assume the later lengthened spring for GT. F

My understanding of the 2 different helper springs comes from a post on "mk1-forum.net" where the 2 were compared.
Both early and later (orange - 21A1806) springs were the same total length but the orange unit has a longer spring section and therefore, a shorter link section than the earlier springs. Orange springs also have thicker coil wire.

My '66 S is No. 1197 so fitted with the early springs. As it has settled, the rear is sitting a bit too high (and nose is down) despite having rear adjustable struts set to their shortest position. I intend to fit a pair of orange springs to see if they pull the rear down slightly and maybe stiffen the suspension too.

Interesting little stretching device - I assume to help clean between the coils?

Bill

Generally, the fore / aft pitching (braking / acceleration) will affect the front valves within the bags more than the rears.

The device is just that - unit expands the spring through turnbuckle for cleaning.