Mark MK

[Funfinder]

Today I was "virtually" at the (formerly?) home of Karl: - Movie "Untraceable" from around 2008 -
and yesterday I found this MK v. 4 (from 1960) user manual - perhaps you like or can use it.

This "audio-frequency-inbalance-circuit" was state of the art in World War 2 but available til 1995 (improved).
It moved from Poland over France to United Kingdom during all these "Nazi" attacks.

[Carl-NC]

One of these was in the White's museum.