This was 1964 in HI. I have no idea what ‘proof’ of marriage was acceptable to the judge. Do you have a citation for your claim that applies specifically to HI for that timeframe?
Sorry, you got that the wrong way round.
The current legal proof of marriage is a Marriage Certificate and it’s the only document that suffices. If it was different in 1964, there’ll be a HI statute dated between 1964 and now that defines the change - that’s how legal systems work. If there isn’t, then it hasn’t changed. Can you cite any such statute?