I might be mistaken. The enclosed photo from an FW hub expert shows that the left nut is also an indicator nut with window. On my Moulton four speed, the right longer nut doesn't have a window like on SA three speeds?
(The photo shows the author's emergency "kit" for getting the hub working just to get home in case the left rod comes undone and flies out and gets lost in which case the hub goes into neutral and cannot be ridden. A clever rod and wedge to get him going again). Maybe a good use of that window in the nut!