Here is a rear-view of my two Plaubel Automatic Makiflex lenses, so you can see the operating mechanisms. On the left, is the 150mm Schneider Xenar. On the right, is the 210mm Schneider Xenar (minus extension cone and board, it bayonets on and off).
On the 150 you can see the iris-cocking lever, about 7:00 o'clock orientation. About 4:00 o'clock you can see the lever that releases the spring-loaded iris, which happens a microsecond before the focal plane shutter fires. At about 11:00 there is a silver push-button, that manually closes the iris.