Eames shell chair stamps, labels, etc- a timeline?  

I'm selling some extra shell chairs and have run up with some questions from buyers because the chairs have no markings.
They had been covered at one point with grey painted backs, my understanding is that dates them to pre 1953?
I've looked around and can't find a true timeline of stamps (or lack of) different feet, bases, shockmounts, and labels. Think we can put one together?
I've included my ad, I'm not trying to advertise, but if someone can help me with dating them better by taking a look, it would be appreciated!
Smooches!
-beks
(edited by DA - link to ad removed - no sales on the forum please)