This is a lighting control, HID lights, outside neon sign lights, inside florecent lightings and EMs. I wounder if a low voltage event could cause this too. I am HVAC guy for comercial maintenance and I had a building loose a leg of power once when I was on the roof doing PM. half the units that tried to start burnt a compressor and when I pulled the cover to one the contactors were trying to pull in and they melted just like this ASCO.
http://www.ascoswitch.com/Products/icp/icp917cat.html
