TheCodeBreakers
5 v w x y z
Each letter may now be represented by two numbers—that of its row and
that of its column. Thus e = 15, v = 51. Polybius suggested that these
numbers be transmitted by means of torches—one torch in the right
hand and five in the left standing for e, for example. This method could
signal messages over long distances. But modern cryptographers have
found several characteristics of the Polybius square, or "checkerboard,"
as it is now commonly called, exceedingly valuable—namely, the
conversion of letters to numbers, the reduction in the number of different
characters, and the division of a unit into two separately manipulable
parts. Polybius' checkerboard has therefore become very widely used as
the basis of a number of systems of encipherment.
Polybius and others never said whether any of the substitution
ciphers they described were actually used, and so the first attested use of
annaabi.ee 
