14 1/2" f4.5 TTH Cooke maximum aperture opening?

[Soomuu]

I was cleaning a lens of mine today and noticed when the aperture is wide open the iris was still showing quite a bit. I'm wondering if this is normal for this particular lens and if anyone has the same lens and would be able to check and see. Lens is a Cooke Series II 14 1/2" f4.5. I've attached 2 photos, one wide open 4.5 and the other at f 16. I could not figure out how to take the aperture ring off to see if it could be adjusted if needed. Usually there would be a screw to keep the ring in position but this one has me stumped. Any help would be appreciated.

Cheers,
Gary

[Mark Sawyer]

I just checked mine, a 14.5 inch pre-knuckler. Yep, the blades intrude about 3 mm into the barrel when wide open. My 13 inch and 16.5 inch pre-knucklers don't do that. On the bright side (no pun intended!), with the front element on, it magnifies the opening quite a bit. Measuring though the front element, it opens to 80mm. so it's still an f/4.60. If you removed the blades, you could get it to an f4.28. Mind you, with the front element off, it's only 59mm wide, so an f/6.24...

Crummy snapshots with the front element on and off...

[Soomuu]

Thanks Mark! Greatly appreciate it. Yep, the opening looks about the same as mine. I was thinking that about the elements magnifying the opening but was not sure because when I measured the actual opening it didn't add up to 4.5ish. I Wonder why they just didn't make the blades retract all the way.