Hello everyone. I was given this lens because the person had no use for it (got it in an estate lot) and knew I liked cameras. The lens clearly states Canon FL 135mm f2.5. However, it bares no resemblance to any FL lens I have used or ever seen (real or on the web). There is only a functioning aperture switch (8 curved blades). No focus barrel or distance markings. In fact nothing twists or moves except the aperture ring. The whole lens body is smooth. The rear of it is a large threaded mount (approx 58mm diameter and about 10mm worth of thread). Maybe a process lens? Can anyone identify this lens or usage? I've included photos of it next to a Takumar M42 for size comparison.