Secret decoder ring

Decoders, whether badges or rings, are an entertaining way for children to tap into a common fascination with encryption, ciphers, and secret codes, and are used to send hidden messages back and forth to one another.

Secret decoders are generally circular scales, descendants of the cipher disk developed in the 15th century by Leon Battista Alberti.

[3] Today, high quality, stainless steel decoder rings for children and adults are being produced by companies such as Retroworks[4] and ThinkGeek.

A "Drogan's Decoder Wheel" is mentioned in the 1985 comedy movie Spies Like Us by characters played by Stephen Hoye and Dan Aykroyd.

[7] Laura Petrie mentions her husband Rob's "Captain Midnight Decoder Ring," in Season 5, episode 27 of The Dick Van Dyke Show.