An actual die based on the sphericon shape. It''s kind of weird because it doesn''t always land with a face upwards; some numbers are indicated landing point-upwards. There are smaller numbers around the relevant vertices to label those. I've worked on making those "smaller numbers" less small, at least on otherwise empty faces; they are now reasonably readable. Also, the numbering now not only has opposite faces adding to 13, but the value of a vertex (for those vertices that can land pointing up) is now equal to the sum of the values of the two numbered faces adjacent to it, or the difference between them if the sum would be greater than 12.
Odd though it may look, I think this die is actually completely fair. All of the faces are identical, the center of gravity is right in the middle, at exactly the same height (potential energy) no matter which face it is sitting on, and the energy to roll from one face to another is just the same for all faces, since it derives from the smooth-rolling sphericon. And in fact six dozen rolls of the die and a chi-square test show no cause at all to reject the hypothesis that this die is fair.