Found this today didn’t know what to make of it at first.
I suppose you want metal boxes too?
I’ll bet $5 that heat come from outside the box as opposed to from within. 
lol…theory…someone try this…
Have a HEAT source near plastic and when it starts to melt does the melted surface melt TOWARDS the heat source.
I thought I read somewhere thats how you can tell the direction of a heat source…someone go try this out…
Actually as it melts the middle and bottom of the plastic heats up also and caves IN against itself bring the TOP part over the top and thus is bends towards the heat source.
That would make sense,
Found this cover plate when I was helping my uncle remodel his kitchen. It was located behind a 26 year old wall oven. We decided to install a metal coverplate after what happened to this one.
I’m keeping this one :mrgreen: