Teleplex is the Master Teacher. Used by the U S Army, Navy and reading, radio and telegraph schools. It is a box with an open hinged lid. On one side is a Victrola-type crank.
Wires lead out to a set of ear phones and a telegraph key.
The reels look to be about an inch or so wide, and maybe three inches in diameter. The man who knows the code is in touch with the world. Become an expert operator, make big money. No experience required. Designed for U. S. Signal Corps.