Nowadays it will most likely be a sheet of A4 paper which you load into your typewriter but A4 is a metric paper size. What would have been loaded into your 1960s or 1970s built typewriter when it was in actual work use? Traditional British paper sizes are defined in inches of course, the equivalent to A4 would have been foolscap folio which was 203 by 330mm (A4 is 210 by 297). However, there were various other sizes, i like that the A5 equivalent called foolscap quarto is also known as "kings"!
Interestingly, despite being the paper size of the British Empire and Commonwealth, foolscap folio has a German origin. The name foolscap is from the watermark of a jester's hat used to identify it. The actual foolscap size is 337 by 419mm, it is folded in half to make a folio page. Then in half again to make a quarto.
Foolscap folio is still available, i might get some so we can compare it to good old A4.
