Thank you for viewing. The exterior shows some signs of use, but I believe it functions properly. In preparation for listing, I confirmed the input (INPUT), output (OUTPUT/BYPASS), and operation using a 9V battery and an AC adapter. The rubber part of the back cover has deteriorated and is slightly discolored. Also, the rubber bushing for the screw that opens the battery box is missing. Please check the images. Immediate purchase is welcome. I will ship it on the same day of purchase if possible, or at the latest, the next day. Thank you.