Covered under a 1923 patent, this Doere Topum duplex blade putter has two faces, and they both have negative loft.   Harry Doerr believed that negative loft on a putter could give the ball topspin.  However, unlike the developers of earlier negative loft clubs, Doerr was also interested in achieving greater consistency on long putts. According to his patent, by giving the concave face a radius much greater than “that of a golfball,” the shaft could be tilted back, away from the target, and the ball struck at its center instead of above it, thereby eliminating the overspin naturally imparted when using his putter in a normal fashion.  Not sure how well his design actually worked, but judging from the great rarity of these, not very well.

This 35” shaft has a solid wood Huntley-style grip that is grooved out to receive the golfers thumbs.

This is the actual Doerr Topem putter shown and described in TCA2 v1 page 299. It last sold at Sotheby’s NY in 2007.