Wasn't it Fraktur in printed materials? I studied physics in the early 2000s and we still learned the convention, but rarely read anything that used it. To me, the incongruity of using an archaic font in a fast-moving science like physics was fun. Probably convenient at the time (early 1900s) because printers routinely had Latin and Fraktur fonts available. Germany was the country of physics around 1900, even the journals were in German! Some of them still have German names to this day (even more so in chemistry), but the contents are all in English.

I can kind of read Fraktur - my motivation was that we had an old (1930s or so) crafts book at home that I wanted to read. I cannot read Kurrent or Sütterlin. Not only do I not know the letters, they all look so damn similar! I would've noticed if these vectors or matrices had been printed in Sütterlin, because I'd have had much more trouble reading them.

I don’t remember what was used in printed materials. Probably Fraktur as you suggest. In high school we used Latin letters with arrows.

At university in the 1990s, they gave us a photocopied sheet with handwritten Sütterlin and Greek letters in the first lecture. The professor wrote the lecture notes onto a blackboard and we copied them by hand. It was definitely Sütterlin. But I believe nowadays people use Latin letters.