He has a two-pip die on his website, that he says is the minimum number of pips required to be able read a six-sided die. I think you can actually get away with just one of the corner pips on the 6 visible, say the pip in the corner where the 2 and 3 meet.
- Pip is not visible, even on the side faces: 1
- Pip is in the top right of one of the side faces: 2
- Pip is in the top left: 3
- Pip is in the bottom right: 4
- Pip is in the bottom left: 5
- Pip is on the top face: 6
You can also make a 20-sided die with only the one marked. All you need for a die with any number of sides is one face marked with an orientation indicator, and you can figure out the positions of the other sides from that.
