I made a wrong connection in finishing off restoring my Heathkit IT-11 capacitor checker, which caused the full 600 volt B+ to be applied across this old 560 ohm 1/2 watt carbon comp resistor:
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Enormous amounts of magic smoke came out of it, but after ~50 years of waiting the original glass fuse did its job and opened maybe about concurrently with me hitting the switch on the bench supply.
Once the resistor cooled down it split right in half with just the slightest poke.