The problem with authenticating signatures is that people profess to be able to discern a real signature from a fake one. The simple truth is that it is nearly impossible to determine whether a signature is forged or not.  Years of signing habits need to be observed and the person being studied must not use several different signature forms.  Some things that affect changes in signatures include:  being rushed, a severe mood change, whether the situation is a legal or personal, whether the atmosphere is formal or casual.  I firmly believe there is no way to tell a secretarial from real signature unless TOLD by the person writing that this is being done. 

I've used my own signature as an example of how signatures change.  I never write the same way twice:  No one does as a signature is much like a fingerprint.  There are no two exact matches unless the item is a preprinted (a copy). Beware of those claiming with 100% certainty that they can tell you if a signature is fake or not.  Even handwriting experts who appear in court cannot tell the judge that!  Case in point:  The Jon Benet Ramsey case.  The most we can do as collectors is give an 'educated opinion'; but that's all it is, an opinion.



Top Left:  This is my slow and deliberate legal signature.  When I write my full name, Suzanne, I ALWAYS put a B, then my last name.  When shortening my name, I never use the B.  HOWEVER, I've a tendency to use two different style "S's".   I haven't realized when I use one over the other yet.  It's a mood thing.  Sometimes the loops in my first S are way pronounced and go far (example NOT shown).  The middle signature shows how I write when the paper is put a certain direction.  This happens in cramped spaces or when something is blocking my hand (like the spiral on a notebook), like if my purse or something is on my left arm. The signature on the bottom is when I am tired, when I don't care, am bored, or just in a rush! I bet if I signed some of these sig and I was as a celeb, you'd think it's secretarial or fake.

Try  this yourself.  How many sigs do YOU have?