I have a short note/letter written by Woodrow Wilson and signed. It belonged to my grandfather. It is dated Nov 19/89 and reads "Will you be kind enough, if your rules permit, to give the bearer of this a card and book for Mrs. Wilson?"

The letter measures 8 inches by  2  5/8th inches. 

To my eye, the signature is identical to one from a similar time period currently listed on Ebay (http://cgi.ebay.com/WOODROW-WILSON-AUTOGRAPH-LETTER-SIGNED-01-04-18...). 

I would like some advice about this, in terms of potential value and whether or not I should pay to have it authenticated, and if so, who is reputable. 

If everything works out, I may list it for sale to free up some cash to expand my vintage fishing lure collection, another of my hobbies. 

Thank you to everyone in advance!!!