The Tonebender MKI circuit is one of my favorite fuzz circuits and one of the rarest fuzz pedals. Luckily for us, builders such as Seeker Electronics are making the circuit in modern times, as finding a vintage pedal is highly unlikely, especially without a price tag that would make even the avid collected blink.
Knowing how many original tone benders inventor Gary Hurst made is impossible. The first run of them was made in wooden enclosures. Gary then switched to metal-pressed sheet metal enclosures that were painted gold.
The MKI as we know it only existed for about a year, from 1965-1966, before the MK1.5 came out, which had a considerably different sound.