In the 60's there was no consistent standard for this. I remember this being written about in the CACM 1967. Those with access to old copies of the Communicatio

In the 60's there was no consistent standard for this. I remember this being written about in the CACM 1967. Those with access to old copies of the Communications of the ACM can take a look at [1]. Here is the title and abstract: Towards standards for handwritten zero and oh: much ado about nothing (and a letter), or a partial dossier on distinguishing between handwritten zero and oh, by R.W. Bemer The Chairman of the ACM Standards Committee, Julien Green, has charged me with making “more effective use of CACM for communication … to get grass-roots opinions from the ACM membership.” This paper is the first attempt. A partial dossier on distinguishing between handwritten zero and the letter oh is assembled here. This presentation was triggered by a request for guidance in this matter presented by the United Kingdom Delegation to ISO/TC97/SC2, Character Sets and Coding, at the meeting in Paris on 1967 March 13-16. The matter is just now in the province of USASI X3.6, to which comments might be directed. Comments will be expected within sixty days [by approximately October 1st]. [1] https://dl.acm.org/doi/10.1145/363534.363563 https://dl.acm.org/doi/10.1145/363534.363563