To my knowledge both chairs are before 1963. The 7 Serie (3107 and it´s variations 3207/3117) dates from 1955. In 1963 FH changed the cap on the bottom for the first time. The ones on your chairs are first generation.
In 1975 the changed the original 4-wheel base to they 5-wheel base in case of security-standards.
Thats a great chart!
There are a few variants missing though, but for a basic guide its perfect.
To the thread started i would say that the green chair is slightly earlier than the other and is from the 50´s.
The black one is late 50´s/early 60´s in my opinion.
If you are in Europe and need to "get rid" of them i am all ears.
Love these early chairs.
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