I recently found my class photo of the elders school I attended in 1977. Sam Friend was the New York emisssary who conducted it. My guess is that in the 70's, 90% of all the dress clothing worn to the meetings, male or female, was made of polyester.
I myself had ties, dress shirts, sport coats, slacks and suits of the stuff. Yes, even a leisure suit in a coral color with contrasting white stitching.
If there had been a fire the entire congregation would be melted in a huge gob of plastic.