Wow, I just had to google that and some people in a convo on wikipedia say they were taught to put two spaces as late as 1990. Personally I never encountered that (I've seen people consistently not leaving a space quite a few times, but never consistently two).
Was that practiced only in typewriter typing, or also in books? I should check at my parents' place tomorrow, the oldest printed book at my place is from 1966 and definitely only has one space after a full stop.







