Charles Blathwayt's British patent dated May 15, 1894 covered a triangular-shaped head, the sole and both faces making up the three sides. However, he included the possibility of forming the head of the club to obtain two striking faces at suitable angles. The patent illustrations show a triangular shape head like this club, with a right-handed putter face and a left-handed lofting face. Blathwayt goes on to state that he can include opening on the head so "I can fill up the interior recess with any suitable material, and so alter the weight of the clubbed to suit varying circumstances." Three illustrations place the opening at the top of the head, the RH face, and both the RH and LH faces.
Blathwayt included the possibility of integrating a wood block into the head, so the head could have one or more wooden striking faces, which is what he used to fill the openings in the faces as shown in his illustrations. Furthermore, he notes he "sometimes forms the base [the sole] with a concave or convex face, to suit the particular stoke required."
In short, Blathwayt reserved the right to create and/or fill a recess in the head in order to adjust the weight of the club. With this iron offered here, I suspect that he placed the opening at the bottom of the head to make the club lighter and, using a short hosel, more in line with the weight of a normal iron as was made in the 1890s. He then inlaid the wood to provide it with a solid sole as was originally designed and shown in all the illustrations. The fact that he would form the sole with either a convex or concave shape could easily explain the concave bottom half of the left-hand face on this club. A concave iron blade was once thought to be useful, but that idea faded with the passing of Willie Parks Jr's. concave face patent lofter, another early 1890s iron.
The auctioneer does not know for a fact that the 36" long duplex iron offered here was produced by Blathwayt, but the chances are great that it was. The head, which has been reshafted in recent years, fits the 1890s, and its design fits the language and illustrations in the patent even if the exact illustration of a wood-filled sole is not included. Both faces are covered with hand-hammering marks. While the hammer on the LH face formed its concave lower half, the hammering all across the RH face is extremely unusual, with no readily understood purpose.
Whoever made this club would have known that iron putters had smooth faces. Maybe it was hoped that the hammer marks on the face would give the ball traction, call it an early effort to provide the face with a form of scoring.
No matter who made this iron, it's extremely rare—the only known dual blade duplex iron with a wood inlay known to the auctioneer. The only club that the auctioneer has personally seen that comes close to this iron is the single John Raddell iron pictured and discussed in The Clubmakers Art v2. p524. Patented in 1928, that iron has two mirror-image blades, with a hollow space between them, so it can be used both left- and right-handed. George Forrester also produced a duplex iron in 1896 that was hollow between the two blades, but the auctioneer has never seen one. Truly, dual blade irons are about as rare a club as there is.
For more on the Raddell, Forrester and Blathwayt duplex blade irons, see TCA2 v.2 p.524.