Well the bolt on version comes from this manual. Fitting instructions. Romoto 3 Standard. Model 5 ser 3 Special with axel extensions on base and axel housings Model 5 ser 3 with axel extensions on the base but with ser 2 axel housings. Now if that hasn't confused you another pic for you to study. So afer all that I dont know what conclusions could be made if any apart from the fact the clip on toe ring came before the bolt on, so, 1st- Romoto 2/2a 2nd- Model 4 3rd clip on. 4th bolt on. still an interesting and possability althouh slim Model 4 Special with no badge, recoil starter