Here is a clean, 1948 Captain Midnight, SS (Secret Squardon), metal decoder.  The decoder was used to send a secret message at the end of the radio show to inform the listener about next week's show.  This decoder is metal (brass I think), measures approx 2." in diameter, has freely spinning decoder knob (dial) on front with two (2) dials on back with smaller, inside dial being more difficult to turn.  Overall condition is very clean on front with some wear/pitting on back.  Please see the other vintage decoders I am also listing.  I combine shipping.  Thanks - Howie