Here is a wall clock, the dial numbers of which are not Arabic and neither Roman, but are presented in the form of a binary code. Clocks are approximately of 25 cm in diameter and operate only on a single AA battery. To be guided by them is not difficult, even for those who do not know the binary as each digit of the code is exactly on the same place where the original number should have been, so that time can be determined very simply by switches position.
These unusual wall-clock costs 40 bucks.