Re: Standardisation is always welcome
I'm nearly sure computers simply used the teletype terminals to start with as keyboard + printer combo. Those didn't have the \, so they used /, (1950s to 1970s, note while TTY33ASR is 1963, electric keyboards produced Morse tape at least in early 1930s and the TTY and Telex non-morse Telegraph type services started in 1932, with even RTTY before 1945. Originally Teleprinters used the ordinary phone lines!
The TTY33ASR was used on computers, like a typewriter, it had / but not \ (Zoom in on the image, you can read all the keys).
I don't know how | (pipe, was ¦ only an IBM thing?) was typed.
(also interesting, https://en.wikipedia.org/wiki/Bit-paired_keyboard )