a=the
French ship=market
sailed from New York=price
sailed from Boston=quotation
to-day=is
for Marseilles=any even number
for Bordeaux=any number with a fraction

With such a code, a German spy in New York could cable a seemingly harmless message to a friend in Holland, such as:

“The market price is 110.”

That would mean, of course:

“A French ship sailed from New York to-day for Marseilles.”

Whereas a very slight change in wording:

“The market quotation is 110¾.”

would mean:

“A French ship sailed from Boston to-day for Bordeaux.”