Looking through my 'stash' of old inserts that have come from a variety of different sources, I came across an unopened pack of form 210 dated 1984 in Personal size.
I believe this insert was also available in Deskfax size as well, which would make more sense.
I'm not a music composer, so I don't know how much music you would get on to a page like this.
Are any of you music composers?