From memory, the production version had a slightly different smokebox and headstock (the bit that holds the fork). Then some of the later ones (but not all) have a fore and aft fork which isn't so good looking.

I have a feeling that you cannot take the prototype one out of gear but all the subsequent ones you could.

good to see the sir john William out and about

Different headstock to later simplicites, but can take out of gear.

Many thanks guys, cracking little engines in my opinion

Great to see another simplicity out and about. Would be good to get the two of them back together some time.

An excellent rally with a great selection of engines - always nice to see some new ones. Masham was celebrating its 50th anniversary.