I have a A4 poster from Star Wars: A New Hope with 17 Signatures on. Looking to sell it

Hi Guys. I have a A4 poster from Star Wars: A New Hope with 17 Signatures on and I am looking to sell it. Although I do not have a certificate of authenticity, it was purchased at Glasgow Comic Con last year and was fully confirmed all the signatures will authentic and all signed on the same day (same pen throughout). However, i have been unable to find out all the signatures, and do not know where i could take it, or email a photograph to find out, so i know the proper value. Any suggestions? Thanks a lot