The original Mare’s Leg Pistol was a shortened .44-40 Winchester 1892 lever action rifle which featured in the ’50s TV series Wanted: Dead or Alive. Its distinctive design featured a cut down butt stock, shortened barrel and large cocking lever loop.
Since 2005 JB Custom have been look-alike that is registered as a pistol with the BATFE so it can be legally owned without jumping through NFA hoops.
Steve Doran has produced a video review of the pistol. It looks like a lot of fun!
The standard model sells for $1695.