At the end of Back to the Future 2, as well as the beginning of BTTF 3, right before the Doc and the DeLorean are struck and sent back to 1885, Doc and Marty are communicating via the walkie talkies which, at the time, (1955), were the only ones like that in existence. One with Doc, one with Marty. However, in the scene at the drive-in, the Doc gives Marty two walkie-talkies with new batteries. Where exactly did that second walkie-talkie come from?