Seriously Joel, I compared yours the in-persons over at
http://www.starwarsgrapher.com/heroesvillanssw.html
And I did not see anything out of the ordinary, it may well be a real one, if you are assuming every autograph from Frank TTM is a secretary, why did you even bother to write to him? Unless you found out such after you already sent it off. Who said his autographs TTM are often secretarial? I can't find anyone other than just vague opinions and no one ever seems to say WHY they think they are secretarial, other than they "heard he had a secretary signing for him".
Again, I just don't see much of a difference between what you just got and those at:
http://www.starwarsgrapher.com/heroesvillanssw.html
Even the word "Yoda" looks dead-on with in-persons. Show me these so-called "small but critical differences." Please explain in detail, because I don't see them!
http://www.starwarsgrapher.com/images/600_oz,_frank_2.JPG
Compare the above in-person with yours, where are the real differences? Other than normal handwriting fluctuations everyone has.