I still don't understand why they use a ferrous back plate, seems like a heat bottleneck, a copper alloy could be made strong.
I do wonder if the gold coating is a big part of the heat vehicle, they bond to the blocks with indium foil that is a good carrier of heat and has a low melting point of 157 C, but still I would expect the back plate to be non ferrous and something like copper or copper alloy.
I've been tossing out bad diodes for years now. Never thought about collecting them. Didn't know until today that the diodes were iron containing. Magnets for your dead soldiers. :crackup: