I recall that Cliff Robertson and David Soul (AKA Det. Ken Hutchinson of 70s TV's Starsky and Hutch) starred in a good rendition of this code method in a TV movie, "The Key to Rebecca" (1985).

Dunno if it was ever released to tape or disk, but it was a pretty good flick nonetheless. It was a WWII movie, taking place in north Africa, pitting an Allied Maj. William Vandam (Cliff Robertson) and decoder Alex Wolff (David Soul) against the well-known, well-respected, much-feared Axis General Erwin Rommel (Robert Culp), and the breaking of the numbers code of the The Desert Fox through finding that a few of the radio points captured all included a certain romance novel entitled Rebecca.

Dan