I found a 50mm 1.2 at a local antique shop for a good price, however it possibly has some mold on the rear element. I only had the time for a quick glance since the store was closing, but the rear of the lens was covered in a yellowish substance that looked like you spilled something and let it dry. There was also some yellow stuff growing on the light seal foam on the inside of the camera, above the mirror.

My question is, is it possible to have this cleaned off if it is mold? Obviously I'd like to add a 1.2 to my collection, it would be my first. Thanks guys.