Eames swivel dowel question  

I was hoping get some info on the production years for this chair. Iʻve looked online and on previous threads but Iʻve seen inconsistent years of production. One thing is certain in that it does not have a rope edge, but the shock mounts are larger (2nd zenith?) Anyway, any help is appreciated. Attached is a few photos, one is a close up of the shell with a round marking where the back bends into the seat.
mahalo.
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