New member and very much a novice collector

It is definitely not authentic, I have seen other military vehicles discoloured in this way. I think it must have been left outside, or in a damp environment, at some time and the brown residue has formed on it, see the picture of an old 666 Corporal Missile I used to own. I hope this helps Dave

Many thanks to Jan & Dave for your further observations. I will continue to display this 'rogue' model and put it down to (in)experience. David

The important thing to do is to ENJOY it, Dinky Toy collecting is fun and completely harmless. Dave

...and expensive!