Please help ID these 'Egon Eiermann' style chairs  

Hi everyone,
I've bought this set of six unlabeled 'Eiermann' style chairs. The chairs were most liekly produced in the 1950s/1960s in Germany.
But I am wondering about some differences to all Wilde+Spieth Eiermann chairs (SE68) i could find.
Diferences are:
- places of the screws fixing the seat on the base
- the way the steelframe is welded at the bottom of the seat
- top of the frame holding the backrest
have you any idea there were other manufacturers than Wilde+Spieth producing chairs that similar to the Eiermann SE68?

thanks 😉
Michael
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