You are in NJ, the Met isn`t that far !! Try looking online and see if you can find an email address for them !! Since he was curator there they would be the most knowlegable about his work especially since they have some of it !! Send them a couple of good pics !! Or just give them a call tell them what you have,, they may know how many were done !! The fewer that were produced the better !! They may be able to help you confirm it !! Make sure what you have before thinking about selling it !!