When I was at the one in Kitchener, the children's museum had some of the maze geocoins for sale. Geocoins are unique for each maze.
e.g.
GPS Maze - The Children's Museum Geocoins
Mine was "Maze Series#06 - Kitchener Ontario 2009"
I only discovered them as we leaving the museum, so I bought a couple
I also managed to get most of the codes of the geocoins that were on display.