Doc's walkie talkie was one of a pair of Archer Space Patrol walkie talkies that Emmett Brown bought new in 1985A, while Marty was at Biff Tannen's Pleasure Paradise Casino & Hotel interviewing Biff about Grays Sports Almanac, and which they took with them back to 1955 to enable them to keep in touch while Marty retrieved the almanac. Doc had his walkie talkie with him when the DeLorean was struck by lightning and accidentally sent to 1885, then sealed it in the Delgado Mine along with the DeLorean for seventy years.