Yorkie's ace observations in the comments about this mystery toy racing car and its possible use as a Century 21 prop were so good that I had to post them.
Yorkie said that in the Stingray episode 'Man from the Navy', the World Navy Sub 27 is a converted racing car toy or model. A conning tower has been added and the rear of the car becomes the front of the sub. It could be the toy pictured.
Yorkie said it also appears in Thunderbirds painted red in the episode The Man from MI5.
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Woodsy adds:
Since posting the 'mystery' racing car post I've realised where I first saved the picture from. It belonged to modeller Mike Delamar and I asked to use it nearly 10 years ago on an online thread. You can see the thread on the Eagletransporter Forum [you may have to register after a while]. Mike's a master scratch builder and the old thread detailed his search for original parts to create the World Navy Sub 27 from the toy racing car. Sadly the thread peters out and the finished model is not shown.
See what you think anyway: