It was Douglas' sporting model and so represented the top of the range and most expensive model, excluding the I.o.M. model. So naturally they did not sell as many OC models as they did the more economical 350 and 600cc EW.
Production figures do not survive, but the highest frame number known is 413. So starting at #100 (typical practice) just over three hundred in the two years it was on offer.
-Doug