Well...haha...wouldn't ya know it...it arrived and there is more fungus than met the eye. I don't know that I can blame the seller, its hard to see, you have to get a bright light on it at juuuuuuuusssst the right angle but there's a half dozen spidery spots. They probably don't affect the image much, but after I expose it to sunlight for a while I may have to attempt a cleaning.
If it's that hard to detect, there's a better than good chance it hasn't etched the lens yet. If it's a simple lens assembly, I would immediately remove the element and soak it in the ammonia/peroxide solution. That should not only kill it, but remove it.
Its a Sekor S 75mm f3.5. I'm not sure yet which surface its on, or if it can be accessed. But its so damn dry in my house that my humidifier can't even keep up so I'm not worried about it getting worse until I figure it out.
I put the front element under my dissecting scope...haha...there's a lot of fungus, and I suspect a lot more that was cleaned off. There may be spider lines etched into the coating on the rear of the element. Almost all of it is near the edges of the element so I don't know how much it will affect images. I got it all cleaned up and the lens looks mostly great now. But there's also what looks like a helical scratch on an interior surface right in the center of the front element, which you should see if you look closely at the pic below. Its almost like a golden spiral. Its very hard to see this in hand.The image is before I cleaned it
I think it will be fine. The rest of the camera is in Excellent ++ condition
No really, it is. Hard to believe its nearly 70 years old, other than the previously fungus encrusted lens. I'm going to shoot a test roll or two tomorrow.