Pictured below are two Christopher Reeve signature's typical of his late 70's early 80's signature. The top signature is 100% authentic. The bottom signature has some noticeable similarities and also some noticeable differences.
The question is this: Can you determine the authenticity of this signature by recognizing non negotiable signature traits regardless of variation? After all, we know that signatures not only modify over time, but also change according to the situation in which the autograph was received.
With that being said, is the bottom signature a genuine Reeve signature or a forgery? Please feel free to expound regarding your justification either way. 
Tags: Authenticate, Forgery, Reeve, Signature, Superman