Drew, the earliest ads I've seen for the D-W pad are from 1929 --
D.W. Recoil Pad, American Rifleman Feb 1929.jpg
and show a 1922 Patent date.
In 1911 a Silvers was about it. My 1912 SD&G catalog only shows the Silvers pad and my 1915 H & D Folsom catalog only has the Silvers and the Grieb. The Silvers in those days was curved and had a spur --
132280 18.JPG
There were several different rubber slip-on or leather lace-on pads, Akron being a popular brand.