If you collect Convention materials or nostalgia memories, perhaps you'll find this lot of interest?
These convention badges are made of a puffy soft vinyl with a clear pocket in front w/a piece of stiff board to write your name on & slip it into the pocket (see photo). These are attached by a rubber necklace to put around your head to hang the badge for all to see.
There are 6 badges, 1 wooden nickle & a tin pin back button advertising the MDA (Magic Dealers Asso.) convention in May of 1975