My question to the group is based on the uncertainty of buying a used lens. If you see a lens for sale, what clues do you use to verify the lens cells and the shutter aperture scales match? Sometimes, this is stated in the sellers info but other times it has to be spotted in the pictures. I see a 100mm lens currently being sold mounted in a shutter with the scale for a 135mm/400mm convertible lens without any mention of this discrepancy. This is an easy one to spot but what if you want a 150mm f5.6-f64 and the shutter originally mounted a 90mm f5.6-f64?

The newer copal shutter scales have more info but it is not as clear as when states the lens (Nikkors). Is there a site that list the various copal scale codes to the intended lenses?

I did search around but couldn't locate a discussion on this topic.
Thanks everyone.