It's a really rather advanced use of typography (making borders) for such a simple machine that didn't even have parentheses. But yeah, it's plausible, and I li

It's a really rather advanced use of typography (making borders) for such a simple machine that didn't even have parentheses. But yeah, it's plausible, and I like the authors theory that it was intended to be a vertical bar, but it was replaced with three dots to avoid confusing it with I and 1.