Quote Originally Posted by summicron1 View Post
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.