They were indeed called Tressy dolls and were around in the early 1970's, certainly 1974. They had a bubble cut hairdo with a long centre tail that was wound in by a key in the back and let out by pulling gently whilst pressing a button in her stomach. I had a brunette, my sister a blonde one. She broke the blondes' neck, whereupon the hair no longer worked, so she stole mine.. I don't think I ever forgave her.....

The new Barbie 'Rapunzel' doll uses much the same sort of technology but has an extension as well to make it even longer.

LTS