Mamiya Universal 65mm Lens Aperture Question

[Photobop]

Hi all,
I just picked up a Mamiya 65mm for my Universal Press camera. When I set the aperture to wide open (f6.3) the blades in the lens do not open all the way, they appear to still be closed just a slight bit. I can't find any info online, but I found this video and the aperture on the lens in the video does exactly what mine does. You can see at about the 50 second mark that he opens the shutter and the aperture is clearly still closed a bit despite being set wide open to f6.3.

Everything else about the lens seems perfect, and there is no oil or grease on the aperture blades.

Does anyone have experience with this lens, or does anyone have one you can check and see what the aperture does at f6.3?

Much appreciated.