I believe these were made by Earthquaker Devices. Two channel overdrive. One is a germanium transistor, the other mosfet. They share an EQ but have independent gain/volume controls (and their own “cut” switches”) so you can use it reasonably well as a rhythm/lead kind of pedal.
When people talk about how amazing the tube screamer is, this is why I expect it to sound like. Pushing your amp over the edge at all frequencies, not just that nasal mid nonsense.