I have a pre-AI version (135/2.8 CQ), which I converted to AI. Lovely portrait lens with smooth focusing and nice warm colours. If you are not a pixel peeper, those old lenses can be a treat to use, but the modern lenses are usually better for digital cameras.
Bought it for a tenner, broken diaphragm-
so I got an angle grinder, and sawed off the mount.
That also left me with some interesting bits of glass-
the front group in particular project the maddest looking images,
but unfortunately, it’s not really useable.
And not an easy thing to disassemble.
I do have a 50mm AiS, but I haven’t tried grinding that one.
So I can’t really compare it to the Ai-
well I’m primarily looking at this for use on my FM2n. I also bought a TC-201 AIS 2x Converter earlier today on Ebay, which I think should work okay with this.
I lent mine to a friend, will only get it back in April. If you can wait a few months, I’ll lend it to you, and you can make up your mind.
As far as I can remember, mine cost €40 or €50, but there wasn’t a single scratch or mark on it, it looked like it was brand new. For €100 I’d expect an AI or AI-S in excellent condition.