This is from the time when most audio equipment had two prong AC plugs, and the prongs were the same width. Connect this device from the chassis ground of a piece of audio equipment to the ground of a wall socket. Try the AC plug one way, then reversed. This device will let you know which position is correct. Yes, you can do the same with a voltmeter. This is in the original box and with the original paperwork. Always stored with the battery removed. No scratches, three very minor scuffs on the front. This can ship USPS Priority Mail in their Small Flat Rate Box. Asking $35.00. See one image in the Gallery. From ZIP 18661.
