Bertoia chair manufacturing sites  

Hi all,
I'm new to this forum and am excited by the quality of the questions, answers and participants that I've seen. I have been doing research for the past few months regarding the history of the Bertoia chairs, the various manufacturing sites worldwide and the evolution that the products have undergone over time. Also, the subtle differences between the US made chairs and those produced in various other locales.
So far my list of manufacturing sites include Argentina, Belgium, Finland, Sweden, France, Germany, Italy, Japan, Switzerland and, of course, US. Some of these are subject to verification. What I'm interested to know are details pertaining to these sites, distinguishing differences or markings and particularly dates of production.
If you have information that you're willing to share, I'd be most appreciative.