The SunTour Hole Shot was conceived as a derailleur for BMX bikes. It was designed to operate over a two speed freewheel.
Obviously inspired by the Coelacanth, SunTour tried to incorporate as much dinosaur DNA as possible. Despite being produced in 1980 it is a sliding rod design, with the pulley cage moved by a bell-crank reminiscent of Simplex’s designs from the early 1950’s. It mounts on the drop-out, but operates under the chainstay - this time in a curious echo of the 1950’s Altenburger and even older Nivex designs - although in anticipation of SunTour’s own S-1 and SX-100 designs. The single sprung pivot is on the opposite side of the guide pulley from the tension pulley (not between the pulleys as would be more normal) - again an echo of the Altenburger design.
Quite why BMX bikes should need such a radically unique design is unclear to me - but that is true about many aspects of BMX - a sport that is rivaled only by golf in the eccentricity of its rituals and dress code. ‘BMX - the golf of youth’ - now there’s a slogan.