I took the gas burner assemblies out of a pair of 1910 headlights tonight. One burner was held in by a screw, washer, and square nut. The other, a really good condition light & apparently original, was held in the same way, except the screw was short and not extending beyond the square nut and was soldered together with the nut. It made a very tidy fastening. The solder was slightly domed above the nut. Was this original practice, and if so, in what years were the burner mounting screws soldered?