VINTAGE DYNAMIC TUBE TESTER by The Jackson shop Electrical Company {Model 648-S}

Product Name: VINTAGE DYNAMIC TUBE TESTER by The Jackson shop Electrical Company {Model 648-S}
VINTAGE DYNAMIC TUBE TESTER. I have not tested it and do not know if it has been calibrated. For full disclosure, I plugged it in, and I can hear the machine power up, but the needle does not move. It is old and has been untouched for years. It's a collector's item and one that shows some wear and tear on the outside case, but looks in great shape otherwise. See pictures.. This belonged to an old electrician friend who left it to us and we are hoping someone would love this as much as he did. Either a fellow electrician, collector, or both. :) Made in the USA, around the 1960s. Measures shop approximately 16” wide, 14” long and 6.5” high.