This question concerns my newly acquired Mamiya RB 150mm C Soft Focus lens. This is the lens that comes with 3 disks.

On this lens, there is a lever to close the aperture to the set value. On all other Mamiya lens, this lever goes to the end and when I let it go, it springs back. On this particular lens, as I move the lever, there is a definite friction point toward the end, and if I go further, it sort of "clicks" and stays there. I am guessing this "hold" feature is implemented to facilitate focusing, as this lens needs to be focused with aperture closed to around f/8. Can someone confirm this is the case? (or your lens does the same thing?)

Thank you.