As previously noted (but see below):
'The Blue series of Action transfers came in two editions; one had the full 18" background, the other a cut-down 15" background. As you can see from the two covers shown here, both were described as "Big". The 18" had the traditional three-panel structure used previously, whereas the 15" edition was simply a piece of card folded in half.'
As it happens, we've never been able to obtain an unused 18" edition of this set for scanning; the above background was pieced together using an unused 15" background & a concatenation of unused areas of used 18" sets.
And yes — I am quite pleased with myself, thank you very much.
Below is the 15" background as it was originally, showing how much difference a little snip here & there can make.
Picture Credit: the SPLAT Scan Archives, with thanks to StellarX (7 Wonders)
© Tom Vinelott 2023