As to the plastic - It is not stable and warping of some level is found in every example encountered, and there seems to have been three main issues; plain greys (light and dark), silvery-grey or aluminium colours, mottled/swirling mixed-pellet, and plain but bright colours (red, light and dark blue, pink and British Racing Green), .
It's my belief that they were probably issued in that order, with the greys made from clean material before the war before wartime proscriptions/restrictions, then the mottled examples from 'recycled' plastic and finally after the war - but from the same set of moulds (hence the early/pre-war aircraft types) - the more colourful ones which match the later helicopter addition.
The 'Welly', with a close up of the wing markings with "', one of the plain metallic ones (photographed at Sandown Park toy fair) which I think may pre-date the mottled ones, but I could be wrong, they may well go together with the coloured ones which I - myself - think are later?
Warping - as can be seen in the photo's, is not as severe with these silvery ones.
Please use our in-site search engine to locate exactly what you're looking for or call 01202 417171.It must be said though - this is pure guesswork and it may be that the mottled ones were first and all the plain ones part of a second 'tranche'.Other reasons for placing them earlier than the post-war dates I've seen given to them is that A) had they been issued in 1955 (one date ascribed to them on a forum) they would have been more up-to-date types ( began injection moulding in 1941, the probably date for these, as you would reasonably be expected to experiment with a new technology by making a cheap toy you could get some return on, if it all went a bit Pete Tong!My role was to act as umpire and to take the photographs.Stepping into our time machine, we dialed back to the summer of 1969.