Chronogram

Webster's Dictionary of the English Language

·noun The record or inscription made by a chronograph.

II. Chronogram ·noun 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.