Shorted vacuum tube filament

I bid on some 7027A vacuum tubes and out of the three, two were good and one had a dead short from the grid to the plate - NOT something you'd want to plug into your equipment! So, I had a little fun and ran the filament up to 22 volts until it broke. But, like low-wattage filament lamps, sometimes the filament breaks and shorts to itself, creating a bright mini-filament. Here, the filament no longer heats the cathode, but creates a bright incandescent light under the working part of the tube when plugged into my tube tester at its normal 6 volts.