Chronogram

n.
  1. An inscription in which certain numeral letters, made to appear specially conspicuous, on being added together, express a particular date or epoch, as in the motto of a medal struck by Gustavus Adolphus in 1632: ChrIstVs DVX; ergo trIVMphVs. - the capitals of which give, when added as numerals, the sum 1632.
  2. The record or inscription made by a chronograph.