I remain of the opinion that it could, or could not, be genuine. The big question to my mind is the HS prefix before the KSS. I have never seen this before BUT if the frame is genuine then it is one of the very first swinging arm HS frames produced at the time the very first swinging arm non-HS frames were produced. It would be easy for them to get confused in the factory so the HS prefix just could be genuine. What is certain is that someone has worked on the bike to fit alloy hub sliders to single sided hub forks (or vice versa). I have seen this done before but only by a serious Ariel enthusiast - which doesn't help us one bit with this question.
36 4G, 37 VH, 53 ex ISDT KHA (project), 54 KH(A), Healey 1000/4 (project)
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist once more - but not Machine Registrar.