One of the most sought after antique golf clubs, the Spalding Kro-Flite double waterfall F-6 backspin iron has a wavy pattern of large corrugated grooves on its face.  This rare club was offered only in Spalding's October 5, 1919 catalog.  According to the patent issued to William F. Reach, the wavy lines would allow the golfer to impart a great deal of backspin to both a direct stroke and cut shots.

The Back of this iron is marked with Spalding's Crow & Kro-flite Trademark and "F.A. Peebles, Special." The sole is stamped "F-6 Mashie Niblic." The shaft and grip are original. This is a beautiful club.

TCA2 Vol 1, p. 274-275.