😍 For all the designers who've ever toiled away at specs and style guides like this (i.e. financial research report templates, investment statements, etc)
They do have a well defined approach to legend text on charts. Scale, title and subtitle, key to symbols, source (rare these days with people"borrowing" other people's work) & breathing room (margins) for the chart. There is a bit more reference lines than I would use, but 1920s!