Barcelona chairs. Varient? Origin?  

I think you have an older reproduction here. It is clearly not a Knoll production.

This is probably one of the most copied designs of the 20th century, and there are far more fakes out there than real (at least 100 to 1, probably more like 1000 to 1). This forum gets at least one person per month, asking about this chair. The age of the chair is really irrelevant, since the Barcelona chair was designed in 1929, I am sure they were already making unauthorized copies back in the 50s.

I am far from and expert on the details of this design and the lineage of producers, but most of the details you show (sloppy welds, spotting on the chrome, pop rivet in the joint, etc.), I would place my money on it not being real.

By the way, you should really search the forum for "Barcelona chair", and there are pushing up on 100 posts that discuss all the aspects of determining authenticity. I am sure that you can make a determination from these.

Sometimes, no or slow response to an ID request here is due to good manners.

Your chairs are poor-quality knockoffs. The cost of having cushions made for them would be greater than their value on the collector market. Your actual mileage, of course, may vary.

Please don't take my assessment the wrong way or as unsympathetic.

I basically assume that all Barcelona chairs and all Wassily chairs are fakes. And probably every one I have seen in person has been a fake.

Incidentally, not all stainless steel alloys are non-magnetic, but at room temperature all non-magnetic steel alloys are stainless.

Thanks to all the comments. I was about 90% sure these were knockoffs ( I do have a very nice white reproduction one that could easily be mistaken for Knoll). It just seemed like they were not even trying to keep it within spec of the original(and after a couple hours searching I couldn't find a match online), so it was a bit or a curiosity