Mamiya 90c lens. Cheap. Has small amount

I've 2 90c lenses for RB67. One has a peripheral discoloration on the inside
of the rear element group. This disappears stopped down one click. I have
tested the lens and it shows no discernible effect of this blemish.
Otherwise lens is very good, speeds perfect etc.
I would sell this lens cheap to someone who wants it.
It has not deteriorated in the year I've had it. They usually don't. I don't
know if the thing is lens separation, or some kind of stain, but you cannot
get at it, as the rear elements are glued together (I tried. I'm good with
lenses).

Make me an offer.