This is a vintage MXR Distortion +. The logo on the surface has mostly worn off, but based on the internal pot dates, I believe it's a 1978 box logo model. It's from a period known for its fat low end. Although it's labeled as a distortion, the gain isn't extremely high, more like an overdrive. I found it useful for boosting the distortion of my amp, resulting in a thick yet articulate sound. Functionality has been confirmed. There's a little scratchiness in the pots, but it's not something I find bothersome. I also purchased this used, so I can't say for sure, but it appears that none of the internal parts have been replaced. While it has some cosmetic issues, the sound is undoubtedly fantastic. I highly recommend it to anyone who doesn't mind a player's condition. Thank you.