I have no idea how accurate this is, just randomly pulled from the web. https://lecycleur.com/style/the-righ...ntage-bicycle/
"Prior to 1975 there was hardly any noteworthy alternative to cotton bar tape. Synthetic imitations with interesting surface finishes were spreading on budget race bikes and randonneurs, but for high end bicycles cotton bar tape was still the standard."

I am, however, stubbornly biased toward one wrap of cotton and a couple good soakings of shellac.