Old design, this one purchased circa 1995
(steel, 12.75 inches)

To take the ring off, push the horse shoes together while twisting at the same time, so that they line up and the ring can come off (and reverse this idea to put it back on); here are photos of this process for the Wing It version of the puzzle:



"Wing It", copyright ThinkFun 2003.
(metal and plastic, 5.5 inches, 2.25" diameter ring)