Moller 71 - under seat  

Something else has come up.. do upholstered 71's come with a plywood seat covered with foam or are they generally a suspended material with foam on top?

 Picture of my chair below. It was leather, dense foam, then plywood base nailed to the chair frame.

I have not torn apart many of the upholstered JLMs, but the ones I have torn apart have always been a stretched nylon for the support (not plywood), and they have always had leather or textiles terminated with tape or trim around the edges (never fitted with dust covering).  I am far from an expert on the subject, but I would bet that these were previously re-upholstered.

Thats what I was thinking, but when I took the chairs apart there were no other hole marks in the frame.. only the nail holes from the dust cover and leather that I removed. Nothing on the outside at all either.

I was the person that responded to your message elsewhere. As @zephyr said, and as I said before, the current upholstery and seat support is not original. If you need an additional opinion on this matter, @spanky is definitely the authority on Danish upholstery and has, undoubtedly, worked on more Moller chairs than any of us.

It's odd that you didn't find any other tack holes, but I can say for sure that that's not Møller quality work on that upholstery.  They would not have tacked on the bottom edge of the rails like that and their tacks would not be so unevenly spaced.  They'd all be in a neat line, all about the same distance apart. And as Zephyr said, the line of fasteners (usually staples, while we're at it) and the raw edges of the upholstery material were neatly covered by a black cloth tape, like old-fashioned bookbinding tape.

I can't explain the lack of other holes or marks, though.  That's just odd.

Thanks for all the help everyone.

I'll take a closer look tonight on the outside edge. I am guessing the best way moving forward is to knock off the plywood seat and have them redone as originally intended. 
 What would be a good modern fabric to use for suspending the seat? Assuming standard-ish dust cover isnt strong enough. (I stripped them, but dropping them off at a shop for finishing)

When I get home, I will check my photo archives for the last set of JLM 77's that I converted from upholstery to Danish cord to see if I have any photos of the upholstery and construction before taking them apart.  It was a few years ago now, but I may have taken some pictures, I am weird like that.

This being said, I would default to Spanky's knowledge when it comes to upholstery and danish chairs, every time, and it is nearly as good as any picture...

After a quick online search, I found this video which explains a lot to me.

https://www.youtube.com/watch?v=_eQLvQRsrkA

Dust cover, jute straps, ~1.5cm foam and then whatever fabric. Certainly looks better than the piece of plywood nailed on that I have! 

Not that it really matters, but popped off one of the plywood seats and zero markings or holes to show these have be redone at some point of their life. Very odd. Would Moller have sold blank frames? Apparently the previous owner brought them over to Canada when he moved from Europe. 

so this is my first try uploading to this new forum format, but I will give it a try....

staples were on the out side of the stiles and rails

used a lot fo spray adhesive to get the foam to stay...

I believe there were staples on the inside, combined with spray adhesive, keeping the upholstery fastened...

Also, sorry, I could not find the photos of the 77/57 project I did last, only these 55/71 that I did before that.  which were the photos of the inside I think.  Still have both sets, but they are all corded now.