Im Unsure of your familiarity of the starter knob Jonesy. (Re Your query/uncertainty about the end of the starter handle on the Bitsa) Im sure youve seen them apart,but Just in case Ive included some Images for the thread,since I dont think we have a starter or knob image as yet . This Starter is from a model 5 With its use on the Model 4 yet to be Confirmed...The Model 4 starter difference is the exclusion of the visible spring retaining pin on the left. The internals are also the same with a few minor exceptions,Brass(early)or stainless carrier washers,and 2 different Pawl styles,but really they are the same.