As the tittle says, this pedal is a clone from MI-AUDIO 'Crunch Box', which takes the circuit from a hot-rodded Marshall JCM 800 itself (I think!). It is made by argentinian brand "Cluster". Unlike it's Aussie counterpart, this pedal delivers the same type of distortion but more mid-focused, so it sounds more warm, valve-type, which for me makes it... ¡even better!. I like to use it mostly through the input of the solid-type amps clean channels, and combined with a TS9 on the front for a valve-type sustained sound.
EDIT: if you are interested in using this as a preamp, bare in mind that the sound loses a lot of the few treble frequencies it has in drive pedal mode. You might need an eq. pedal to correct/compensate that.