fake barcelona chair with knoll stamp ?  

So, I heard back from the person I contacted at the Knoll Museum (figuring they'd have the best records of marks?).  She said, "This hasn't been easy. I met with KnollStudio VP of Operations.  We discussed policies in the past.  She said the "signature" stamped on some of our KnollStudio pieces has changed over time and has been the discretion of the Director of KnollStudio. She said it would be so hard to track what has been done and when. 
"Although honestly the one font I still find highly questionable.  I hope this helps. "
The lack of kerning alone is enough for me to doubt it but I'm no expert, that's for sure.  Oh, and the fact that the seller said that the chair was recent issue, yet the mark is really different from current issue chairs on the Knoll site.  Those two things.  

this is officially fascinating....

Surely there's someone in the Knoll organization who could categorically rule out the singe-font, badly-kerned example.  Thanks for your investigation !

Well, I wrote back to that person and thanked her for checking into it and then simply said again that it didn't seem likely that a chair that was billed as being made recently would have a mark that is so different than the ones shown on the Knoll website. I didn't expect a reply but she wrote back right away and agreed with me 100%.  
I have a feeling that the people in the other department didn't think it was very pressing.  Maybe it's  not but I know that some manufacturers take counterfeiting very seriously.  It's something I can get worked up over very easily.  You know---because it's WRONG.  
(I also love doing side-by-side comparisons of just about anything.)

Unfortunately companies themselves or people working there often don't have much interest compared to design nuts here.
Unless you get someone wh has a passion for design most are just employees there doing a 9-5 job trying to sell product and don't particularly care.Making effort to follow up a query that is not related to a sale I would assume is likely irritating to many of the staff.Who knows how many emails they get or will get in future with people thinking they found a gem now this chinese made junk will end up on the side of the road or in charity stores.
That is my experience anyway and a totally understandable reality.They are mass producing companies after all.Even so considering the explosion in Chinese copies I would expect any company to make at least a little effort to archive their history of manufacturing and to collate answers to queries for future reference.
Firma did say they would remove the 2 chairs in question and was going to follow up Knoll so from Europe maybe we will get a different opinion.I will advise if I hear back anything.

Thanks to Vangelis and the DA investigative team. Outstanding thread!

i was looking on ebay and i found this :
http://www.ebay.com/itm/original-Barcelona-Daybed-Ludwig-Mies-van-der-Ro...
it has the same signature and the same fabric under the cushion as the fake barcelona chair , also the small cushion is very diferent compared to the authentic....another fake ?

I think someone who is in the business of making fake Mies van der Rohe furniture realized that items an incised mark will fool a lot of people who are leery of unmarked Mies stuff. 

The difference in quality of metal and plating is readily apparent in those two leg close-ups . . .

That's what I thought too, SDR, but then I noticed that the floor under the leg on the right has a texture and that what looks sort of like a roughened surface on the leg might just be a reflection of this.  

And in case the fake-looking mark isn't enough, the end of the cushion is indeed different than that on the real thing.  The end piece is a flat circle of leather on the fake one, whereas the on the real one it is a strip of leather that is gathered into pleats in the center.  The button on the fake one is also smaller in relation to the diameter of its cushion. (This makes it look like the cushion is too big in diameter but it's actually correct if you compare it to the thickness of the big cushion.  Unless that's too thick, too...)

Well if they are fake Knoll legal could follow up Firma as well as the Ebay seller frankfurt-minimal to back track where they have been sourced as both items are being sold in Germany.
If they are fake stamps they should investigate and nip it at the bud now.
The roll cushion on the daybed certainly looks sus with the cheap looking end detail and the wrinkled skin close up looks more like the leather on a fake.