Leica Summitar 5cm 1:2 Prime lens

Leica Summitar 5 cm 578087, 1943

The outer lens ring of this lens was threaded on too far and blocked the diaphragm ring. After dismantling, greasing and cleaning the blades, the outer ring must not be screwed back on too tightly. If screwed on too far, it produced incorrect apertures (no reference point for the outer lens and next) and (again) blockage of the diaphragm ring.
This could be solved with a shim ring of, for example, 0.03 mm between the outer lens ring and the next. See drawing. The marking (°) for the front lens should be threaded to the marking f 3.2 (becomes 2.2) and not further. The lenses are clear, no haze, no fungus. The extending mechanism, diaphragms and the sharp helicoid work perfectly. Provided the above is observed, the lens is fully operational.