Roy,
First of all, Doane is dead. I'm not sure of date of death, but you
might want to check this out, especially if the signature you have is
also dated. To find an authentic signature you can try a Google search
using "signature Gilbert Doane" as you serach words. I have found many
examples using this process with other authors. I don't think there
will be much value in a signed copy. Most of the genealogy researches I
know do not collect resource books for value, only for reference. Of
course, I could be wrong. You might try looking on eBay for other
copies, and try www.addall.com to see if any book sellers have signed
copies for sale.
Les