Supertwin
This machine could be late 1960s or early 1970s based on the UK design of the time, the one in Malcolm's video is actually the last iteration of this machine although operation is fundamentally the same. It may not have the additional insert on the top of the agitator (to give a more powerful wash) as I believe the similar Simplicity (Canadian) models had a two speed motor to differentiate between the two washer actions. My Supertwin is actually the quietest of all my twin tubs, and I consider it quiet and smooth.
For $50 I would say go for it, AND GO NOW!
Al