Two Bertoia side chairs... real or knock-off?  

looks real to me
post a photo of the bracket where the seat attaches to the base

Here's a photo of bracket
I think this is what you're referring to. If not let me know.
http://s1352.beta.photobucket.com/user/margauxpeaches/media/IMG_3154_zps...

If they are real
Why would neither the chair nor cushion have a Knoll stamp? It would mean they were pre-Knoll manufacturing them? Also remembering hearing somewhere Knoll will verify if a piece is real or a knock off. But is that only if it's a post-Knoll chair?

real.late 70's or early 80's...
real.late 70's or early 80's edition.

Look fine to me. Knoll didn't...
Look fine to me. Knoll didn't stamp the chairs until a few years ago.

they are real
they are the real deal. nice find not get to work with a wire brush and clean off the rust

Look good to me. Knoll didnt ...
Looks good to me. Knoll didnt start stamping these chairs until very recently and the seat bracket mounting the base to the chair has changed serveral times through the course of production).
Very fine wire wool, auto-sol (chrome polish) and a bit of elbow grease works a treat for getting rid of the pitting and bringing the chair back to life!

Not sure
Can you post some photos of the whole chair from different angles?
The welds are very sloppy. I guess it's possible that it was repaired.

Additional images
Here are the images you asked for of whole chair from different angles. Thanks everyone.
http://s1352.beta.photobucket.com/user/margauxpeaches/library/

Hi
The shape looks correct, so I would say they are most likely authentic. I just have not seen a chair with welds like that before.