"Every operator develops a distinctive style of sending so that he can be recognized readily by those who work with him constantly. [...] Mr. S., a dispatcher of much experience, works daily with forty or fifty men and states that, after hearing four or five words, he can readily recognize the sender, or be sure that he is not one of his men."
Bryan and Harter (1897) [https://grants.hhp.uh.edu/clayne/HistoryofMC/Bryan&Harter-1897.pdf]