Signed Copies...Rare?

Yesterday I received a book in the mail ordered from Abe (Letters from a Self-Made Merchant to his Son - Written in Gregg Shorthand). I purchased it based on the seller's written description as no photographs or scans were available. I was a little miffed when I unpacked the book and found that it's quality was not accurately described. But I was pleasantly surprised to find that it was signed by John R. Gregg in 1904 (I have attached the scan).

Is this unusual to find books signed by Gregg? I don't think that the seller realized that it was signed because it was purchased at a very reasonable price.

Attachment: Signed Copy Low Res.jpg

(by rdd331 for everyone)