My newly-acquired Mamiya-Sekor Z 110mm f/2.8, which was used to take these recently posted images here, here, and here, has fungus in it.
A lot of fungus.
It was described as “mint” by the seller in Japan.
To his credit, he has sent me a replacement lens. It’s not quite as nice cosmetically, but the glass is clean (other than dust, which all of these Mamiya RZ lenses seem to attract in great quantity).
Yet, I wonder if I should keep and pay for the eukaryotic-exotic first lens?
It seems to perform spectacularly.
Myco-graphy anyone?
—Peter.
Prosophos 
When I saw your first three images, the first word I had in mind was “Fungus”.
😀
(Just goes to show how little bearing the cosmetic condition of a lens has on the visual impact and emotional appeal of the final product!)
-M.
Ain’t that the truth.
Ahhh….the seasoned film guru picked it up! Wouldn’t expect anything less.
As for me…..zero idea that was the case!
Well impressed. How did you see fungus in these pictures?
Andrew and Ken, Mark is joking.
Of all the people for me to have missed that hint of sarcasim…from Mark. Oh dear…Im slipping ☺!
Yes, I absolutely was joking…I had no clue. The images looked phenomenal to me!!
-M.
Keep it and get it cleaned would be my suggestion. If it is a difficult to source lens, I would take it on the chin and get it serviced and cleaned. I did that with a Flektogon that was in awesome condition other than one spot of fungus. It was worth the cost to preserve it.
I would clean it anyway, because fungus can spread to your other lenses (or so it is said), and you probably don’t want that 😉
Prokaryotic problems are worse 🙂