1) The NFHS and NCAA Men's numbering rule was the same in the early 1960's as it is today for NFHS and NCAA Men's/Women's with two exceptions: a) The jersey numbers 1 and 2 were illegal, and b) A team could have both a 0 and a 00 at the same time.
2) How do I know? I remember from watching games when I was young. My H.S. basketball and golf coach (he was my sister's H.S. golf coach too) and a charter member in 1948 of the Trumbull Co. Bkb. Assn. (Warren, Ohio), an association I have been a member of since 1971, and his family were our next door neighbors. Meaning I saw a lot of boys' H.S. basketball games before I ever stepped on the court as a Jr. H.S. player in the 1963-64 season.
3) The oldest rule book in my basketball officiating library is the 1963-64 NBCofUS&C (National Basketball Committee of the United States and Canada), the predecessor rules committee to the NFHS and NCAA Men's/Women's Rules Committees.
MTD, Sr.