Prime Time Watch
Algebra geeks and numbers freaks rejoice: The Unemployed Philosophers Guild has divided the clock face and devised a watch just for you. The Prime Time Watch depicts time solely through prime numbers. Where the digits of our day do not comply with the laws of divisibility only by themselves and the number one, prime numbered mathematical equations are substituted. Four o'clock becomes two squared. Ten o'clock, five times two. And twelve o'clock, the worst offender of them all with a whopping six divisors, is re-finagled into two squared times three.
Aside from its mathematically mind-blowing face, the Prime Time is a completely normal looking black watch.