The TB Mk II has a lot in common with the Fuzz Face and other germanium fuzzes of the 60’s, but it adds a transistor stage in front that increases the gain and moves it beyond the overdrive/distortion realm of the Fuzz Face.
The Deimos project is identical to the original Tone Bender Mark 2 except for a couple of enhancements. First, a voltage inverter circuit has been added so you can use PNP transistors with a standard 9V supply. Second, it includes trimmers to more easily dial in the optimal bias voltage without having to swap out resistors.
David Main from D*A*M Stompboxes has written up a history of the TB Mk II that’s far more comprehensive than anything I could pull together, so you would do well to check out his history page.
A vintage-accurate version is still sold by Macari’s, having been painstakingly recreated by D*A*M. It uses the exact same sandcast enclosure as the original and all NOS parts. The downside? It costs $620 USD (£399 GBP)—a bit more than the £12 it originally sold for in 1966.