Today in 1969, US Patent 3438531 A was issued, an invention of Raymond L. Millard and Arthur W. Tschannen, assigned to the Adolph Coors Co., for their "Plastic Bung For A Beer Barrel." There's no Abstract, although in the description it includes this summary: The invention comprises, in essence, a bung plug having a circular wall section sized and tapered to fit a standard bung orifice, and an oversized, tapered, conical skirt at the leading rim of this wall adapted to guide and subsequently lock the hung in the orifice.