Thanks. Here are some pictures. I am not good at photographing lenses nor am I good at spotting the dust on them!
This is the Nikon F mount version, less weatherproof than the others.
The inner cap is 52mm and the outer cap is 65mm (squeeze).
The first two images show the lens at all but very close focus.
The other two show it at closest focus with the lens extended.
The closest working distance is about 23cm at a field of view approx 75mm wide.
_2184560_DxO.Rayfact 90mm f4 on A7r3 1024.jpg
_2184564_DxO Rayfact 90mm f4 on A7r3 1024.jpg
_2184567_DxO Rayfact 90mm f4 Cllsoest Focus on A7r3 1024.jpg
_2184572_DxO Rayfact 90mm f4 at Closest Focus on A7r3.jpg