Super Angulon 90mm f8 fstop scale off kilter

[rachjak]

Newbie here, acting on LF photography fantasies stimulated by the images of Thomas Struth. Bought a used (I guess they're all used at this point) SA 90mm f8 for my Sinar F1 in a McDonald's parking lot and didn't notice until I got it home that the pointer on the fstop scale goes well beyond the end of the scale (beyond f8) when the lens aperture is all the way open. Pushing it back to f8, I notice the aperture is slightly narrower than the lens pupil - partially stopped down, in other words. Do I need to find a way to recalibrate the scale? The action in the aperture is smooth, slow shutter speeds test well, glass is nice and clean, etc. I appreciate any feedback.