Yes, that stood out to me too. I recall there being two competing camps in the mid 70's regarding whether to 'slash' the O's or the 0's. In search of who these sides were, I came across http://www.circuitousroot.com/artifice/letters/characters/sl... which is a useful summary.

Some old mechanical typewriters didn't have the Zero '0', one had to use the 'O' character. That's the historical reason.

My dad's old typewriter also didn't have a number 1 key, so you had to use lower-case L (ie, l).

It reads very Danish.

  10 PRINT "TØ BE ØR NØT TØ BE"
  20 READ A$
  30 GØTØ 10