Check out this sweet little Metal Muff! This one is all stock, unmodified, and fully tested. There's a small paint chip but otherwise it's clean and in great shape.
Info from the manufacturer:
The Pocket Metal Muff from Electro-Harmonix is a distortion pedal with a Scoop toggle switch. This pedal features a Distortion knob which adjusts the amount of input gain, and a Volume knob which sets the output level. The Scoop switch provides two settings of attenuation in the middle frequency range. In the up position, the mid attenuation is high. In the middle position the mid attenuation is low. In the down position there is no mid frequency attenuation.