The later JOSTAM Sponge Rubber Pads show the original S.A. Huntley patent date of Apr. 10, 1917, Patent No. 1,222,291 --
Patent No. 1,222,291 Apr. 10, 1917.jpg
actually granted after the Sponge Rubber pad was offered in the 1916 dated JOSTAM flyer I posted above which mentions a leather face.
JOSTAM 1916 02 Sponge-Rubber.jpg
The May 12, 1931, patent date shown on the late JOSTAM Sponge Rubber Pads, Patent No. 1,805,273, shows a base screwed onto the gun stock and other improvements to adjust the pad's resilience. Were any of those "improvements" actually included in the later pads?
Patent No. 1,805,273 sheet 1, May 12,1931.jpg
Patent No. 1,805,273 sheet 2, May 12, 1931.jpg