Hans Wegner Rope Folding chair  

I know this chairs ... very well
Yes, they were from the 60's.
I believe they were sold by Sirocco.
My father had a Tupperware distributorship in Mass (he was later VP of Sales of Tupperware) and Sirocco provided the 'house and incentive gifts'. We weren't rich then (by any means) and much of our 'interiors' came from our warehouse stock of same. I was looking for images of this chair and found the Wegner and the Wels and others similar but ... these are the Sirocco. I am sure of it. I have spent many an hour sitting in them throughout the 60's and 70's. As soon as i can work out the hardware hinge I am going to make a couple in my shop. Cheers, Mitch.

how credible....
I would be very suspicious of a reference like the one from designboom where the name Wegner is misspelled twice, the date of the Marcel Breuer chair is 2 years off (should be 1926) and the one shown on the picture is a copy, and identifies a Wim Rietveld chair as folding when it is not...and his name to has got an additional "t"

Does anyone know how to tell if it's rattan or paper?
Does anyone know how to tell if it's rattan or paper? I have two similar chairs marked made in Japan. I don't know how to tell their age or whether the roping is paper or rattan. Any help would be much appreciated.

Paper is
always twisted, is it not ? Rattan is flat and smooth, paper is twisted and has texture -- as I have known it.

That's easy--
rattan is a narrow strip of a reedy plant that looks like bamboo. (Maybe it is bamboo, I dunno.) It is pretty much flat but with a slight curve to the top if you look at a cross section of it.
Paper cord looks like rope. If you untwist an end, you will see that it's made of two or three strands of tightly twisted brown paper that are then twisted together to make the "rope".

Cord vs Caning
The first pic is of cording - full round, matte finish, very flexible.
Second pic is of caning - flat on one side, half rounded on the other, usually shinier.
Also - I have one of these old folding chairs, I can't remember if its Yugo or Italian made, but it is definitely NOT paper cord. It seems to be some sort of grass cording or rope-like material.

Yeah..
...the Yugoslavian ones are often done in a cotton-y cord type stuff with a braided covering over a core thread, kind of like old-fashioned clothesline. You can see in the photo below how the braided covering has worn off, exposing the core. This stuff doesn't wear too well.
There's also seagrass, which is a cord made of twisted strands of some kind of grass. It's greenish when new and then ages to a lovely golden brown. It looks similar to paper cord but has a lot more texture and range of color within each strand. It comes in many diameters and is also used for baskets, rugs, hats, and all kinds of things.

Not a Wegner
Your photo looks like a rope chair that was sold in the 60s and 70s imported by the Otto Gerdau Co. in the U.S. The item retailed for approximately $40.