Angle drive? The only angle drive speedo I know of was for a Vincent. A picture please.Though Ariels used a PA instrument that was angled to come out of a tunnel at the back, but I've seen seen one in the flesh.
I've just done a quick search on the web and found this;
Smiths chronometric 120mph speedo S.575/3/L which my application list shows is correct for 1956 Vincent Rapide D 998cc Twin 1955-1956 Comet D 499cc Single 1955-1956 and Sunbeam S7 Vertical Twin 1957 and S8 500cc Competition. May also be suitable for other models.
I haven't got a list, this is what someone else is saying about S.575/3/L