Base unmarked, probably American in origin. This carbon filament Christmas lamp is unusual in that it operates at 110 volts and is fitted with a candleabra base. A major disadvantage of these lamps is that they burned extremely hot and the risk of fire was a serious concern. More common 15 volt series wired lamp sets burned quite cooler and were far more popular. Today these 110 volt carbon lamps are quite scarce, probably because they did not sell well.