Mechanical Rowel Spur 18th century German This unique mechanical spur was attached to the left side of the horse and actioned by the rider by means of a cord or leather strap attached to the loop and passing over the brass roller which projects on a flat piece of metal. The rider would pull the strap causing the neck and its rowel to move to the right and roll against the horse's flank. The V-shaped spring restores it in its position when the pressure is released.The purpose of this spur is uncertain. It might have been used by a lady on a side saddle, though this it would have been strange, since using a regular spur on her left foot would have been easier. Maybe this mechanical spur, of which no other example is known, was used by a rider with an amputated left leg.. Mechanical Rowel Spur. German. 18th century. Iron alloy, copper alloy. Equestrian Equipment-Spurs