“A few years ago (2002?) I made this “accessible” cube puzzle by simply gluing/drilling an existing cube. The goal was to get an intuitive sense of “where the cubes went” when a face was turned – by holding the back and viewing the front, the cubist can sense all faces at all times. This makes the design ideal for puzzling in the dark (which I did) but also as an enhancement for the visually-impaired without sacrificing usability for the sighted.
Note that if I had used a simple braille solution with the labeller, the result is quite unusable – a single turn and a given braille character is read as a different letter, if it isn’t already sideways. And reading braille backwards on the reverse of a cube… tricky.
Each face has a unique color, shape, and texture, with the each face’s modification material chosen for ease of recognition relative to the other faces.”