Differences from Herman Miller ea 117 in generations  

Hello,

I'm new to the forum and I have a few direct questions regarding Herman Miller office chairs by the designers Eames.

I've been looking for a suitable (preferably colored) Herman Miller ea 117 for quite some time, in the old generation with height adjustment using a rotating spindle. Now I ask myself a few questions about the execution of the chairs in the different years of production. On the Internet I find chairs that are attributed to the 60s and 70s and have a rocker, which only holds the seat with two triangular sheets (see first photo), and there are some where the rocker is a little more airy, like it is the current models have (see second photo). Now I ask myself:

Were both variants of the rocker function produced in this way in the 1960s and 1970s?

If so, which is the more original variant? or was the seesaw of the second variant subsequently renewed?

How have the Ea 117 (turning spindle variant) models changed over the years in general?

Wie kann man die Produktionszeit eines Stuhls möglichst genau abschätzen?

Wie ist die Struktur der Nummer, die jeder EA-Lehrstuhl hat?

Ich weiß, dass es viele Fragen 🙂 Ich bin nur ein absoluter Neuling auf diesem Gebiet. Vielen Dank im Voraus !

Mit freundlichen Grüßen Fredrik