With no markings or provenance at all, the origins of this revolver are a mystery. Its features all point to the 1880s or 1890s, and someone clearly spent a lot of time working on it – but we don’t know who. What makes it interesting is the very unusual operating mechanism. It is similar to a “zig-zag” system like the 1878 Mauser or Webley-Fosbery, but with angled splines on the cylinder instead of grooves.
The knob is a cocking system (phrasing)
Ian’s video: [7:31] https://youtu.be/NHggIGRdvCg?si=
Exactly what I was thinking. It looks custom built for someone with a hand deformity or injury.