Artists And Signatures Question.

I've had photos of coins signed by the designers or have obtained the signature separately (like on a 3x5 card) to be used with a display of some sort. I think it's a neat sideline, but it doesn't seem to be all that common, so there likely isn't any developed market out there yet. I have Alex Colville's signature on a 3x5 and I was happy to get that since it was his 1967 coins that got me interested in the hobby so many years ago.