I just got a second hand fluorescent light ceiling fixture. Very pristine condition externally, both the fixture and the external electronics. Certification marks are in place, and it's manufactured by a known and trusted manufacturer. I was just detaching the small plug from the end of the cord, when I noticed that the inside of the plastic plug case has a small lichtenberg figure, e.g. a singed lightning mark. It's a surface mark that hasn't corroded or greyed out the inside of the case in a general sense, it's more like some lightning lines about the strength of a lead pencil mark. No detectable smell. No flickering or buzzing of the light when I tested for a short while. The wires seemed to be connected alright. By the looks of it, the mark is not one of subsequent sparks but a one time phenomenon. Is this normal or should I worry?