Yes it does. One of the set screws is missing, but I've made sure the other two are tightened down well. In the meantime I hope it'll behave differently once the lighter fluid dries completely overnight.

A portion of the inner wall of the lens, just behind the front element, seems to have a mechanism that controls how much the lens is stopped down when the button is pressed. Presumably it is controlled by the aperture ring; but currently no such connection, if there is one, is functioning.