Strange Unique European Revolver

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.