[Herb Concord Ca]

A few comments. From the picture, the needle zero is off to the right of zero. To adjust first take a damp cloth or paper towel and wipe the plastic meter movement cover. Leave damp, this reduces static charge on plastic cover, then with a small blade screwdriver turn the plastic slot near the center bottom of plastic case to zero meter pointer. As it has a set pot that Kurt mentions, there may be a battery inside the unit. Turn unit over and see if it mentions an internal battery. Enjoy the dwell tach meter.