I wasn't around in the 70's but like sky high said peoples tolerances would have been alot lower back then when they first started smoking compared to now, 30-40 years later. So when an old head says he smoked the most potent "blank" back in the 70's or 80's from "wherever" there tolerance was alot lower back then and got them alot higher. I read that thread that Texas Kid posted by DJ Short and he said the most potent bud he smoked was from that time, but in the 90's when he wrote that story his tolerance has to be alot stronger. I'm not trying to take anything away from DJ, he is on a level way above me when it comes to growing and smoking buds, its just I remember my first time smoking some "seedless" when I was 15 and I thought it was the best and I never felt anything like that since then.
Edit: Oh yeah, about the opium dipped Thai sticks, IDK.