Invented in 1941 by John Martin of the Heublein Company (distributors of Smirnoff Vodka) and Jack Morgan (owner of the Cock n' Bull restaurant) as a way to popularize Vodka, Ginger Beer, as well as unload an excess of copper mugs.
For a long time, the special copper mugs could only be found in antique stores or auction sites, but recently the Cocktail Kingdom started selling them. You can find them here.
Garnish: Lime wedge
Build in an ice filled highball glass (or copper mug)
Source: John Martin (1941)