Having seen quite a few different backspin clubs, the auctioneer has never seen one like Rigden's Sure-Stop pitcher. The grooves are deep but not nearly as wide, side to side, when compared to typical deep-groove backspin irons.  In addition these grooves are distinctly pointed, nowhere close to square, on their ends. This iron was likely introduced right before backspin clubs were declared illegal, plus Rigden was not a prominent North American professional/clubmaker. These things help explain the exceedingly rare nature of this 35-inch-long pitcher.