This may be the first rubber pad in the U.S. - Charles Ritzmann "Red Rubber Recoil Pad" in Forest & Stream 9-2-1880
https://books.google.com/books?id=S0khAQAAMAAJ&pg=PA100&lpg

[Linked Image from photos.smugmug.com]

S.W. Silver's Indiarubber Works was established in 1864. "The Anti-Recoil Heel Plate-The Silver's Safety Pad" was introduced in the 1870s.
The first Parker fitted with a "Silvers Recoil Butt" was DH #56553 in 1891.