Albert Percival was issued a British patent dated February 11, 1926 to cover his PerWhit putter.  The blade is convex, top to bottom.  To Percival, the curved blade allowed for more consistent contact with the ball no matter if the player varied the position of the shaft from one stoke to the next.  The curve extending all the way down to the sole would tend to prevent the blade from dragging or clinging to the turf on either the backswing or follow through.

This PerWhit putter shows little use and the stamping is clearly legible on the back of the head. The 34" shaft is original and is stamped "Made in Scotland." The leather-wrap grip appears to also be original.

TCA2 V1: p296-297