Those points are well taken, Doug.
Originally Posted by Doug Thomson
As for whether or not it's oil, I'm pretty sure it is. I know that sometimes older lenses develop a high polish on some parts of the aperture blades that looks like oil (I have another enlarger lens that has that appearance). But this is definitely some kind of lubricant. Also, I've noticed a faint trace of lubricant on the ring surrounding the rear element of the lens. So my guess is that the seller applied a little oil to the lens and, perhaps, overdid it.