Thanks Jack - that means there were two Atoms, at the same time? I wonder what the brand name registration people were thinking.
Yes, vccomm, the radial fins, matching up to the radial fins on the detachable cylinder head, were rather distinctive, but I think there was at least one other British mower engine that had radial fins on the cylinder barrel, and some larger British engines did too. The Trojan's muffler was another distinctive feature. It was just a hollow aluminium casting with no baffles, it didn't muffle much. I packed mine with steel wool, but it burned and blew out through the exhaust hole, leaving a sort of afterburner trail behind my bicycle that it drove via a wooden roller above the front tyre. It was quite a decent engine under load, though its idle was about as bad as you'd expect for a 1950s British 2 stroke.
