This should fit the coin chips from the popular tabletop game Smallworld
See also http://www.thingiverse.com/thing:32253

this should be compatible with the stackable version http://www.thingiverse.com/thing:32255
but I might have screwed up the position of the bumps that are supposed to connect it to its neighbors since I had to design it on its head (just my way of problem solving - I'm sure I could have made it some other way, but I'm still learning)

This should fit 21 coin chips from the Smallworld set.