Here's a small update for this project,
>>3271170Lens Diameter: 13mm
Focal Length: 30mm
Macro Focal Length used on this cap with Nikon F mount: 47.7mm (I think.)
F-stop without aperture: f/2.3
Working Distance: 8.15cm (3.2")
I made a ton of paper apertures and a slide-in holder, on the lens front, so they can be swapped in/out easily. I made this chart of what they look like for my personal reference.
