Thomas Salter produced four colour-coded sets in two sizes; the larger sets contained two backgrounds, whereas the smaller ones each had one of the two from the larger (printed at a slightly smaller size). Got it? There were just four different backgrounds in all, & if you bought the larger sets then you owned all of them.
The transfer sheets were a rather different matter; although the 'Small Green' sheet only contained figures from the larger sheets, the 'Small Blue' sheet did contain SOME new figures.
So if you were concerned about obtaining all the artwork without unnecessary duplication (not that it's at all likely that as a kid you would be), you'd have to buy the two large sets & the 'Small Blue' — leaving the 'Small Green' out of it.
It's interesting that the sheet artwork is pretty sketchy, apart from the figures of E.T. himself: those are quite well drawn, so I imagine they were taken from character sheets supplied by Universal. E.T. appears ten times on the four sheets, in just three different poses (one of them reversed on one occasion).
If you were a casual E.T. fan — but not an obsessive collector — then really it would be enough to get either one of the larger sets, so that you would have all three E.T. poses.
A quick note about the serial numbers (of course): Thomas Salter serials take the form "090/" followed by the set number, followed by a late alphabetical character to distinguish one set from another: in this case, we have "090/192 R" (Small Green) & "090/192 S" (Small Blue). So far, so by-the-book; however, the larger sets are marked "2013-2" (Large Yellow) & "2013-4" (Large Red). I don't currently have an explanation for this aberrant behaviour!
But to be clear: "2013" does not refer to the year, which at the time would have been far in the future!
Picture Credit: The SPLAT Scan Archives
© Tom Vinelott 2020