Merchants' Cost And Price Marks
All merchants use private cipher marks to note cost or selling price of
goods. The cipher is usually made up from some short word or sentence of
nine or ten letters, as:
C O R N E L I U S, A
1 2 3 4 5 6 7 8 9 0
Five dollars, according to this key, would be eaa. But generally an
extra letter is used to prevent repeating the mark for 0. If the sign
for a second 0 in this case were y, we would have eay instead of eaa.