At that time, all Regina freewheels were 5 speed bodies. The 6th cog was screwed into a special 5th cog, I forget the position name, it came a few ways, with straight threading for a 15t small, and various reductions for a 14, 13. Later redesigned for a 12t small or "top" cog. I forgot the position numbers and annotations as finding a regina freewheel service board stocked today is fruitless. Every once in a while a swath of old Reginal cogs comes up on ebay and sells for silly amounts.