Originally Posted by summicron1
no, you can NOT assume that if they have the rabbit ears that they are AIS or even AI, Quite the opposite. All early non-AI lenses have them, some later AIS lenses do not.
An AI lens has the lens openings -- 2 2.8 4 5.6 etc) written in very tiny letters along the back edge of the lens mount so they show through a little window in the viewfinder. AIS has them as well.
There's also a step cut in the rear of the aperture ring on AI/AIS (also earlier lenses which have been adapted or converted) lenses.