This is the TC Electronic Ditto Stereo looper pedal. It's a favorite of Vernon Reid from Living Colour. It has mono and stereo inputs and outputs, and features true bypass. You can even import and export loops via usb.
It's easy to use. Tap the stomp switch once to start recording the loop. Tap it again to stop recording. Tap it again to overdub on the loop. Tap it twice to stop playback. Hold down the switch to delete the loop. The single knob adjusts the volume for the playback of the loop.
This Ditto Stereo is in good cosmetic condition. The electronics work perfectly. The pots, jacks and stomp switch are all clean and quiet. You can power this with a 9-volt battery, a Boss PSA-style ac/dc adapter, or your standard 9-volt pedalboard power supply.