Pentax SMC 55mm f2 manual prime lens *please read description*

Pentax SMC 55mm f2 K mount lens There is what looks like dust/fungus on rear element. I've tried to show this in the third photo. I've had this lens a few years and never noticed this until taking the photos for the listing. So I can say that it hasn't effected images taken or shown up in any images. Otherwise a lovely lens with typical Pentax construction and mechanics