Passports in the 1960’s or so were good for 3 years and could be renewed for an additional 2 years, There is block in the passport to show it had been renewed (or not). Those passports had an issue date in them but no expiration date but an Aviso below it:
In the passport it says (with an arrow pointing to it) IMPORTANT Unless Otherwise Limited
This Passport Expires Three Years From Issue Date
If Renewed, It Expires Five Years From Issue Date.
a note it also had a place to mark wife and minors.
Thank you.