Old Perfect brand, hand held DC voltage tester, Chicago, Illinois. Gauge says it has testing range of -3 volts to +3 volts. The needle floats back and forth as I move the tester. I have no idea how to check the meter for proper operation, and do not know how it works. It may or may not work properly. I am selling this tester as a collectible and not for use. It is being sold as is, no guarantees, no returns, no refunds.