That weird green Mantis - the original Marcos use of that name - was a very trendy car for slot-racing in that era. People like GT Models would produce acetate "blob" bodies for cars quite cheaply, and I certainly bought a Mantis, although whether it ever got a chassis and onto the track is another matter entirely. I think Model Cars magazine, then the slot-racers' monthly bible in the UK, ran a feature on the prototype, which will have helped. The slatted back end has a bit of Miura about it, perhaps.