My newly acquired 2006 MMH came to me with an unknown door code. After doing research I found a poor video on how to find the code. It got me looking in the general area and finally found it. Not sure of other years but on mine it is stamped on the control module tucked back in the center console. I made a better video showing its location. Hope this helps those that have a used model and don't know the code.

ps, if anyone is interested in vintage Geiger counters I have videos on some nice vintage ones I have restored.