Thanks for the replies. My query was in relation to a question posed on a 'modification approval form' required by the UK LAA regulating body. Yes, I suppose I could have asked the LAA what they meant. I am purchasing an Aero Sport AEIO-375-M1S and the LAA think, at this stage, that the engine is completely new. Unless it is flying in the UK already, there are lots of potential hoops to jump through to have it approved in the UK.
This 'new' engine is a cloned engine. Aero Sport had ECI develop the 375 and ECI called it the X-370. Aero Sport sells it as the 375. The only difference from the X-360, apparently, is the crankshaft.
In the worst case, I might have to prove that this new crankshaft has performed well and that there have been no adverse effects on other engine parts due to the different crankshaft. Fair bit of research required, I suspect. Colonial matters are never quite as simple as they are in the former colonies I'm afraid.
I suspect the answer to my original question, is the number '1', as no reduction gear exists between the crankshaft and prop.
If anyone is flying with this particular engine, or knows of any anecdotes relating to it, good or bad, I would be grateful if you would let me know.