Thanks for all of the kind words
Mark-To hang the PSA slabs I used a small(3"x3/4") velcro hanger. There are a lot of them on Amazon. I used the brand Command--one pair easily held the slabs and are easy to use. Saves a lot of holes in the walls.
Phil--As soon as I can find a Matty on a 6/12/39 First Day Cover I'll be all over it!
Eric--I acquired the Tinker/Evers/Chance as is at an auction. No way I could improve the current look so I put it up as is.