[Milsurplus] Foxhole Radios

[Ralph Cameron]

As a current project our local Vintage radio club is going to try and 
characterise some materials used for detectors, including the Gillette 
Blue Blade razors used the Foxhole Radio.

Are any of our chemically inclined members able to define the junction 
material in the Blue Blade which enabled it to rectify. As a detector 
this was sometimes used with a safety pin for contact, other times 
pencil lead was used. It is more of a curious undertaking than any 
monumental research. How did the GI's know it would work?
Thanks for any thoughts.

Ralph
VE3BBM