A few weeks before the Pearl Harbor attack, a pair of strange ads appeared in the New Yorker. They seemed to be advertising a dice game called The Deadly Double. One of the ads showed a pair of dice with the characters 0, 5, 7, xx, 24, and 12 on the visible faces. Above were warnings in a variety of languages: "Achtung! Warning! Alerte!" The other ad showed people in a bunker and explained that the dice game was essential air raid survival gear. The company logo was a suspiciously Germanic looking double eagle.

The ads have a somewhat strange design, but only in retrospect did they appear to contain a coded message. The numbers could allude to the date of the Pearl Harbor attack (12/7), with the other numbers representing codes to be deciphered by sleeper agents in the U.S. The Deadly Double itself was thought to refer to the twin threats of Germany and Japan.

Like many mysteries, retellings of this story emphasize the unknown and leave out crucial facts. The 0 and 5 are sometimes thought to foretell the exact time of the attack, but the first aircraft opened fire on Pearl Harbor at 7:48 a.m. local time. Books on mysterious events like to leave this story unresolved, as though the identity of the ads' creator remains unknown to this day. In truth, it was traced to a game company in Chicago that made a dice game called the Deadly Double. Their war-themed ad might seem like poor taste today, but the numbers on the dice matching the date of Pearl harbor was pure coincidence. Still, it was weird enough that the FBI got involved.

http://theunexplainedmysteries.com/Deadly-Double-Pearl-harbor.html