Today in 1940, US Patent 2193445 A was issued, an invention of Siesel E. Canaday, for his “Beer Keg.” There’s no Abstract, although in the description it includes this summary:

The invention relates to a beer keg of the type in which beer is transportedfrom the brewery to the user and which is designed to be cooled in the original container and from which container the cooled beer is vended from time to time.

In this type of beerkeg a cooling coil is dissition accessible from the outside of the keg for ready and quick attachment to a cooling system at the users place of business.