Type of Cord or Rush Seat ?  

They aren't Møller. They...
They aren't Møller. They look a lot like HW Klein for Bramin. But they don't have the contrasting wood pseudo joints. And the weaving is done in that sort of pattern instead of the standard Danish basket weave on L nails.
I don't know what the material is. Close-up photo? Is it natural or plastic?

There is a type of flat paper "cane"
that you can buy pre-woven in sheets---maybe it's something like that? This is obviously wider than what is used in prewoven, but it does have the same very uniform texture and color. On the other hand, the cut ends look like they're a little splintery so maybe i'm wrong.

it is 12 strand
pleated flat cord. Standard use by bramin AND moller
Never found anyone who makes it today

Ah, is that the wool stuff?
We've discussed the flat wool braid here before. Or is this stuff made of a cellulose material? It looks a little stiffer than the wool braid.

That material
is called split reed / flat reed.

Thanks for your ideas...
Thanks for your ideas everyone.
I think I need to post a real close up of a single strand with width measurement. Now that someone has suggested they might not be natural material I'll have a closer look at that possibility [I know they are 1970s as I've inherited them from my brother and they go with a round expandable, 8 brass hinged leaves fold up Dyrlund table].
I don't have access to the chairs at the minute as they are with a rush seat restorer [who can't identify the material as she'd assumed they were Danish cord until I took them over]

My money's on
split reed, as suggested by kcbrains. The cut ends and the knots and the way the loose strands have kept the shape of the frame look like natural reed. The uniform color looks like rattan without the shiny outer "bark", which is where the color variation is in non-split reed. (Split reed being rattan that has had the shiny bark stripped off.)
Split reed is easy to find. A lot of basket weaving places carry it and of course my old standby, Frank's Cane & Rush, has it in many widths.
I hope your person can replicate the weave! They're unusual and very handsome seats!

Thanks spanky
I've just...
Thanks spanky
I've just checked your reference to a previous forum discussion http://www.designaddict.com/design_addict/forums/index.cfm/fuseaction/th...
Still working my way through it but I've got to the depressing statement
"The nice moller folks just enlightened me:
The material was made from 100% wool and produced in Germany, but that factory went out of business about 20 years ago. Regarding the flat cord, it has unfortunately not been in production for the past 30 years. If you have any further questions, please don´t hesitate to ask."
Thanks, gg
I can't seem to find any further reference to anyone having found the flat cord
David

Your chairs do not look like they
are done in wool tape. The material looks fairly stiff. I think it's split reed. You can google split reed and order a sample from a supplier if you want to confirm it that way. Or take a good quality closeup and post it here. Break off a piece and put it on a plain piece of paper and take a photo as close as you can without it getting blurry. Alternately, scan a piece of it at high resolution and save as a JPG and upload it here.

I concur with spanky in that ...
I concur with spanky in that I don't think it is wool.
And we need closeup photos of the material.

Rattan seating cane
It looks like Rattan seating cane - try a google search and you'll come up with lots of vendors and repairers.

New Photo - Close up
The flat cord is made up of 5 fine strands and is 3/8ths inch wide.

Whoa!
That's strange stuff! Looks like very fine paper cord somehow bonded five strands together. I have never seen anything like that before.

Is this it ?
I've not had much luck on this
One cord supplier has said
'we used to stock this Danish tape material but I'm afraid it is no longer available. The British manufacturers sold the machinery to a company in Spain some years ago, but they have decided not to continue production.'
However I have found an image that looks right at http://yaxinzhiye.en.alibaba.com/product/235686285-213647951/Pieces_bond...
Unfortunately they only appear to supply in bulk to commercial buyers.
Anyway I'm trying to make contact with them