Semaphore Trainer, US Navy

Here is a very interesting device, a Semaphore, or Flag Signaling, Trainer, made for the US Navy Special Devices Center by the advertising promotional firm Einson Freeman, Inc.  

The device is a rotating training card within a card. The "Sender"- view is on one side and the "Receiver"-view on the reverse side.  When rotated to the desired letter by the Sender, he see's which flag/arm position must be taken to communicate that letter.  The Receiver, upon observing the flag/arm positions, can interpret them by rotating the card to match the arm position being observed, therefore obtaining the letter.

Measures ~4 inches square.  In terrific condition given its age.