Knoll Bertoia's Authentic or Not  

Hi
They look authentic. I would suggest trying to get a more accurate weight. 30-40 lbs sounds way too heavy.

its authentic
Those chairs were too difficult for imposters to make. The only company that did had a base that criss-crossed. In the last 10-15 years there have been chinese and turkish plagiarists who use the same base design as Knoll, but the dimensions of the chair are wrong.

pads
Also are the pads leather on top and filled with sometype of sand or could that just be crunchy old foam?

Lenox...
I have a pair of chairs in yellow and I bought a pair of naugahyde seats from the eamesbikini people (knowing that they're not real Knoll), and even though they were cheap, they were not particularly the right color or quality.
during the seni-annual Knoll sale, I bought a pair of real Knoll naugahyde seat cushions and they're brighter and beautifully comfortable.
Buy offical Knoll pads and your butt will thank you.

Pads
It's old, broken down foam. Most early pads were covered in vinyl.

great
When the seller mentioned that the pads were "leather with sand," I immediately thought the same. That is, Naugahyde with broken down foam that could potentially be mistaken as gritty or sand like in quality. Thank you

welds
I had a Bertoia chair once and it needed quite a bit of rewelding. I think it's probably pretty common.