I'd hazard a guess and say that this has been a sustained fault (Overloaded Circuit+ Faulty Breaker?), judging by the colour on the inside of the panel. It's strange how the Neutral/Ground Busbars are still silver?.
They used the 6 moves of the hand rule and tied the two pole breakers direct to incoming. with one of the two polebreakers feeding the lighting loads. The breaker labeled "main" just shut off the lighting loads.
I'll bet one fried chicken TV dinner that the lower left DP breaker had the contacts arcing and get hot enough to burn the housing. No overload, no short.
The FP fuse panel in my house did the same thing. Dryer fuse got hot enough in normal use that I had to use gloves to pull it.
These people are fortunate that it didn't take the house with it. TW
This reminds me of a gas furnace at a place I used to work at. It heated the paint booth. Every day it had to be re-lit by hand. I told my supervisor that it needed to be tagged out because it was electric ignition and it was going to blow up if it didn't get fixed.
It was winter so I was told to go re-light it and they would get somebody to look at it. I walk out there with a little propane hand torch since it was to windy for matches, open up the door (the furnace cover plate had been left off by the previous lighter), and lo and behold the panel is black. There was no insulation on any of the wires and little puddles of yellow and red wire nut plastic on the bottom.
I stepped outside and turned off the main and the gas and told the painters they were going to have to suck up the cold for a long time now!
It amazes me how this kind of problem doesn't burn houses down. How could they de-energize that panel?
This event makes a good case for keeping panel doors closed - this one obviously wasn't, as evidenced by the clean condition of the label. It's a good thing that this fault either burned itself clear, or something opened ahead of it. Does a main disconnect exist ahead of this panel?