I don’t remember that open shirt necklace look in the 70’s, at least where I’m from.
For me it was always faded Levi jeans, boots, tee shirts in the summer and western style type shirts in the winter.
Complete with shoulder length hair, and I never seemed to fit in with the real hippies because I was as far to the right as one could be back then.
That redhead and myself were around the hippie movement to but were never fully accepted for 2 reasons.
1. We wouldn’t do the hard drugs that they insisted you do to be cool like them.
2. We were both employed full time and paid our bills, and didn’t loan/give them money.