Are those Bertoia from Knoll  

I believe knoll didn't...
I believe knoll didn't flatten the wire edges until recently. Also a new addition was to weld the bottom wires (where your legs rest) on the underside of the main contour or outline of the diamond. That was discussed here before.

Aside from the soldering...
Aside from the soldering iron weld job, the most glaring issue is how the base and seat are unified. The photo below is from Wright20th which according to them, a 90's Diamond chair. If you go directly to their site you can zoom into the photo more. Look at the profile chair view, and zoom in on the seat/frame connection. See the horizontal track/rail bar. Iuiu's chair base is seamless (for lack of better word)...no track/rail type connection.
Now, compare it to iuiu's chair. When viewing his/her picture at the site, choose the third one. Zoom into the middle, showing the node connection. It's wrong.
Incredibly bad hack job, or knock-off? I say the later.
Not to say I don't appreciate the seamless base. I've always found the track/rail to be distracting. The seamless base is a cleaner less cumbersome looking chair. I suspect durability is the reason for this added railing, much like on the side chair, where they are perpendicular instead of parallel to the frame.
http://wright20.com/auctions/view_search/HYN4/HYN5/170/LA/bertoia_diamon...

ok just post a few more...
ok just post a few more details about the missing track. it's different from the post above, hard to say, the chair showing is covered with white robber.
http://picasaweb.google.com/THECHINH.NGO/BERTOIA?pli=1&gsessionid=obBLid...

I still think they're Knoll.
The new photos show pretty clearly that the sloppy welds are only around the mounting area and at the edge of the seat -- the spots where welds typically break and need to be repaired.
I think Harry Bertoia would've disliked the ugly seat-mounting rail as much as Woofwoof does... So I think it's reasonable to assume that his original design didn't have the rail, and that it was added later by Knoll.
The mounting system shown in the OP's photos looks much nicer, doesn't it? And it also looks expensive and harder to attach than the rail, so I can't imagine why a knockoff would use it rather than just copying the rail.
I think the OP's mounting system is just older than the rail mount. I'm no expert, but my vote's still for Knoll.

And my vote is still...
It doesn't matter.
The chairs are FUBAR, in my opinion.

Now this has been a fun ID th...
Now this has been a fun ID thread. How can we find out for sure?! I still think it's Knoll. I have a friend who bought a MCM house where the owners left their outdoor Bertoia set. I think they might not have these rails, but I don't remember. Another thing of interest, is that the outside has double wire, like an Eames wire chair. The very first issue was like this, and many people don't realize that. SO many might think that was a copy as well, but it is quite authentic. Herman Miller forced Knoll to use a single thick wire instead in court bc the systems was too similar to the Eameses (which was probably designed by Bertoia to begin with).

Knoll
Modified the design of the wire chairs numerous times over the years. If we don't know the exact date of the chairs in question and have a similar genuine Knoll example to compare, then one has no basis to make a determination with certainty.

I'm on a tight schedule, but...
I'm on a tight schedule, but wanted to address Fastfwd quickly. Wright also sold a 1953 prototype (24k) that clearly shows that little was changed during the transition from prototype to mass production. Notice the "track mounting"?
http://wright20.com/auctions/view_search/BFYC/F57S/363/LA/bertoia_diamon...

Authentic
Although woody's right. Doesn't matter. They've been decimated by some schoolboy welder. Boggles the mind really. Any metalworker should know the difference between a spot weld and a stick weld.
Woof, the wires here indicate a vintage chair. Knoll has increased the girth of the Bertoia series wires over the years. And the assembly has changed as well. I've seen similar.
And Pegboard, you'll be confused to know that some Knoll contract fabric Bertoia pads don't come with labels affixed. I have no idea why.

Not that big a deal.
Diamond and Bird chairs without covers look nice, but they're unpleasant to sit on. With proper covers, I think they look even nicer -- isn't Woofwoof's photo of the blue one pretty? -- plus they're REALLY comfortable.
Put some covers on those chairs and no one will know or care what the welds look like underneath.

thread
now this is what I call a thread!

I'm sorry
But I still think it's dubious.
You can not enlarge the photo for the "prototype" chair WoofWoof linked to at Wright so I had to pull out my copy of that auction catalog, and sure enough that chair had the same U channel (for lack of a better description) bracket between the seat and base as Knoll production chairs. Also, despite the ostensibly hand made quality of the chair in the Wright auction, it does not have big globs at each connection point.
If you concede on each of these points (the wavy or bent wires, the sloppy welds, the questionable connecting bar, the fact that it's not chrome plated, it looks spray painted sliver... and still want to believe it's authentic, what you have is a very screwed up diamond chair.
Unless you have unimpeachable provenance that it was hand made by Harry Bertoia, you can't begin to claim that it's another "prototype".
The added photos show more broken wires at the juncture of seat and base. Fastfwd is right. If you want to use the chairs, you can put a cover on them and go to town. But I'm with woodywood and say at the end of the day it really does not matter. Real, fake, those chairs are FUBAR.
Plus I just like using the expression FUBAR, you see it used all too infrequently.
p.s. Lunchbox, I've seen lots of Knoll pieces that were not labeled. Not only Bertoia chair pads. If I were to venture a guess I'd say it's because they job out so much of their production, have changed vendors many times over the years, and don't concern themselves that much with quality control, branding, and corporate identity especially when filling large contract orders.

Whitespike, That's good to...
Whitespike, That's good to know. From what I read most knock-offs have the double wire and that's pretty much a give away. But I did not know that Knoll actually made them like that in the beginning.

Fake
As someone who has owned many from all periods of production, I have to agree with those who point to this being a fake.
Despite any other issues mentioned, in my experience, you just can't get around that connecting bar/rail.
Knoll just never did it this way I'm afraid.