Covered under Edwin McClain’s December 1928 US patent, this Hagen sand wedge has a dramatically curved face, top to bottom, and a large, broad sole.  Bobby Jones even used one of these in the 1930 British Open.  In 1931 the USGA adopted a new regulation that made any club with a concave face non-conforming.  Consequently, Hagen stopped producing this concave sand wedge.

This example has its original 34 1/2" shaft and leather wrap grip. The face and sole both show wear to the chrome, but the chrome remains over most of the club.  Overall this historic and highly unusual club still looks good. 

For more about the Hagen concave sand iron, see TCA2 Vol. 1 p. 283-284