There are 6 TV Century 21 Specials and Extras issued between 1965 and 1967 and this one is as tough to find as the others (apart from the 1967 Spring Extra) though for some reason I see more copies of this with a horizontal fold across the comic from storage. The values for all these specials are for flat copies. This fold is a significant defect and halves the values at least if it is a heavy fold or by two thirds if it is a lighter but still visible fold (see illustration).
This particular Special, the fourth out of six, was advertised for the first time in TV 21 #61 dated Mar 19th 1966 stating an on sale date of Mar 25th.
Three main Thunderbirds stories, one in colour and one with excellent Ron Turner art. Lots of colour photos of Thunderbirds equipment. Plus My Favourite Martian and The Munsters.
Note: some PR issues may have no value. Selected issues in FN, VF or VF/NM may not exist in some titles.