George Nelson 1950s chair? Surely not...  

I've had this chair for four years now, and I presumed it was a 70s repro of some form...
I'm now advised that this may be a George Nelson design from the 1950s, although I can't verify it.
I approached a replica manufacturer of these chairs, saying that my chair had a relatively agricultural black angle iron base with no stamp, and he stated that if has angle iron with hex head (allen key) bolts, then it may well be a Herman Miller-made chair.
As for the stamp, I was advised that the older chairs didn't always have a stamp- many simply had an aluminium sticker which often comes off after time...
Any enlightenment would be greatly appreciated. I'm still very circumspect about its authenticity...
cheers,
SM
(edited by DA - picture fixed)