I think those fuel valves were made in a lot of different versions for different British aircraft. I think they came in Spitfires, Gipsy Moths, and some others. Mine came from an aircraft parts supplier in the UK and was NOS, in its 1940s box, still sealed up. It is not exactly the same as the one in the Marriott car, but looks the same. My guess is that this was an easy part to buy on the surplus market in the 1960s, so that's what they used. One of the forum members has some of them and is having them refurbished, I think, but the one I bought is the only one I've seen for sale that I can recall. I got lucky.