Robbie, good question !
I never saw that hole with the small screw (after 35 years of using them, pffft). I will ask a friend who worked for Leitz repairing everything they made for photography. He will know.
Patrick, wouldn't you be messing with the automatic focus set-up when you change the position of the helical? Maybe I misunderstood what you meant . . .
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Ok, I spoke with my friend. He says to take apart the lens you need to use the spanner on the rear ring, and you must unscrew this tiny screw to further disassemble the lens. And yes, should the aperture numbers not sit in front when you put it back together you can turn the lens barrel and then fasten this tiny screw . . .
This was him explaining on the phone: "just unscrew it and turn the barrel so you see best the numbers . . . "
I didn't, but I think you can safely do so, if you want. I do think all this has a direct relation with the extension ring and the aperture stopper of the Focomat 1c. Different story for the Valoy II . . .
Michael