TT_O, an easy example (or proof) would be to video tape the jump to 1975 and give the video recorder and tape to your self (the you that has already been there/just arrived). That way you don’t have to jump back and fourth. The video tape and recorder would then be availible to you now. you could send the tape to someone (when you leave, we don’t need any more time-loops).That way there is no danger of divergance in this time-line. Just a thought.