Barcelona Chairs - How to spot a fake
I was looking at a pair today in a consigment shop. They has hex screws holding something together. Is this accurate? Are there any exposed screws on these chairs? Also do all the originals have the Knoll Studio engraving like this chair:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260423681...

Hex Screws
So I have been doing my own research and found out quite a bit about the Barcelona, but I am still stumped as to if the one I saw was an original or not. The one I saw has the hex screws which hold the two side together with the cross support. This is how the early originals were done before Mies coverted to stainless steel and Knoll took over.

Is there any ways to authenticate an early original before the stainless steel conversion or the KnollStudio stamp?

The only screws that should...
The only screws that should be present are on original 1929 productions. Corners of the seat have two small screws per corner.

Thats the extent of my Barcelona screw knowledge.