Anyone who has a Mamiya RB 150mm SF lens, can you confirm this for me?

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.

your "guess" is correct

Thank YOU!

That is correct.. the preview locks at the end of it's travel to allow you to focus.

Glad I could contribute something. Let me know what you think of the lens. I haven't really experimented much with it as a SF lens.

I plan to play around with it soon. My first step is to have my girlfriend model for me, holding a resolution chart and try without the disk, from f/4 to about f/8, then wide open with the disks.

Thanks both for your help!