Today in 1904, US Patent 771495 A was issued, an invention of Florian M. Pfluger, for his “Bushing for Beer or Ale Kegs or Barrels.” There’s no Abstract, although in the description it includes these claims:

This invention relates to an improvement in bushings for bung-holes of beer and ale kegs, barrels, or similar receptacles; and the object of the invention is to provide abushing which can be readily secured in a bung-hole and which will form a liquid-tight joint between its outer surface and the surrounding wall of said hole. With the forms of bushing commonly employed for this purpose it is found that before the barrel or other receptacle is otherwise unfit for use the metal lining of the bunghole will become loosened and permit leakage of the contents of the receptacle. By the present invention means are provided where the grip or hold of the bushing on the wooden wall of the bung-hole may be maintained even after years of use, so that the life or usefulness of the receptacle will be greater than if bung-hole linings of the form heretofore employed are used.