Rob Lifson, of Robert Edward Auctions just came through big time with an unsolicited scan of the easel that was inserted into 1968 Topps 3D Packs. He is the only dealer or auction house that has ever made this particular rarity available to the masses, so far as I know. Horrifyingly, it advises the purchaser to wet the back of the card!
This particular easel will be in REA's Spring 2009 auction. The first reference I ever saw to the easel was in an old SCD ad of Rob's in SCD 22 years ago:
If you can't read that, here is a close up of the easel description:
I have updated my previous post on the 3-D cards to include the new scan of the easel. Thanks Rob!