I chimed in a little late , but all advice given above is spot on, Walt Disney is a very tough signature to authenticate, In addition to various artists that signed for him, His signature changed alot over the years and then there are the inevitable forgeries.
PHIL SEARS is hands down the undisputed authority on Disney autographs and most of the time he can even specifically tell you what artist signed the item. Also a nice fellow too. The last Walt Disney I had was a vintage signature and didn't look anything like anything I had seen before , I sent him a scan, he liked it and even estimated a date on the signature and then made a fair offer to buy it and I sold it too him.
I agree with previous post, best bet on Disney is a signed check or signature from an autograph album that you can be absolutely certain was signed in-person.
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jim@stinsonsports.com