A classic treble booster driven by one silicon transistor. The tone control let you adjust the frequency range from full and bassy, to classic 60s “mid-treble”. In this one, the level control is a standard post-gain volume control, which means the gain always is on max and it is a little dirtier. A different approach is to let the level control adjust the gain. That will mean that it becomes a little cleaner at lower settings, but loud and dirty at full. But either way, it is not a clean boost, unless you roll down the guitar volume a lot. And like all old-school treble boosters, it sounds best in front of a dirty tube amp or an overdrive pedal.
The one in the pictures have a slightly different enclosure, but I also build it in a standard stomp box enclosures. But it looks nice like this I think.
And here it is on top of my bedroom 5W Bugera.