I think there are four types and we have discussed them on here before
1.Pre war civilian disc type with slot for large screwdriver or coin
2.Lock and key type, with two small rivets one each side of the key hole
3.later round convex pressed type which you can undo with your fingers, also used on Royal Enfields?
4.Toggle bar type designed so the weight on the end of the bar won't let it undo itself in transit
Rob[/quote]I think that there are even 5 different types. There is also a type with a large round nut, it looks very much the same as the pre war civilian type but it's different.