Cool... glad you like it.
The Dirt Box was my first pedal. I only made 50 of them, so they're fairly rare. Maybe I made 100, can't remember exactly now.
The circuit of the Dirt Box is very much in the family with the MXR+, but it's more vintage than that. It's actually inspired by the old Jordan Boss Tone and with some fidelity and voicing tweaks. The idea here is that it pre-dates opamps, so instead of an opamp like the MXR, it has a pair of silicon transistors set up in a gain/clipping circuit sort of like a Fuzz Face but run cleaner with more headroom. Then after that stage we have the pair of clipping diodes just like the MXR+. People say that this circuit is the one that inspired the MXR+ and the others that use that general topology. The Dirt Box has a different sound from the MXR+ because the transistors also clip a bit. In the end you get kind of a clean-ish, silicon fuzz face barely clipping and then the MXR+ harmonic content which is the dominant distortion factor. So it really does behave a bit like the MXR+.
The toggle switch that shows a fat and a skinny "O" designates the hi-pass filter. The skinny "O" has less low bass and the wide "O" means there's more bass. That bass content has a big effect on the harmonic content.
... and it's just like any other day that's ever been...