Pirelli webbing widths?  

Your theory on teak matches my theory on teak, and all the information I have come across supports it. Old growth teak certainly had better coloring and grain variation. I think you are missing one piece to this theory however, oxidation. The older the teak, the longer it has had to react with oxygen, which I also believe has an effect on its color. Not sure which has more effect the tree it was logged from, or the length of time exposed to oxygen, I suspect the former.

I have seen wider Pirelli, but never narrower. But this is purely my experience. Note, there was also Rotex, which was DAnish, but I think this was largely the same width as Pirelli.

We need Spanky to weigh in, she has more upholstery experience with Danish chairs than anyone I have ever come across.

There are different varieties of teak trees, too, and it stands to reason that newer furniture is made from something other than the true teak genus. Leif will probably know. You can look at a zillion samples on http://www.hobbithouseinc.com/personal/woodpics

Also, check out afrormesia which I can't tell from teak without looking up the differences every time, and even then sometimes not. And yes, oxidation.

As for webbing, I have seen narrower Pirelli webbing a few times. I always thought it looked like it had been hand cut since the widths weren't perfectly uniform. There's no reason why you couldn't cut new Pirelli to fit the slots (I've also seen it trimmed at the ends by hand, unevenly, to fit into narrower metal brackets). Use a new Xacto blade and metal straight edge and be prepared to switch blades as needed. Rubber dulls blades quickly. Very sharp scissors are ok too if you don't mind it looking hand cut. (Note to anyone wondering about woven elastic webbing: no, you can't trim the width down on this stuff. It will fray.)

There is a Grete Jalk chair (or at least that's what I thought it was when I worked on it) that had narrower extruded vinyl straps originally, done in a zig-zag pattern. There is one extra slot on the back rail. The slots were closer to 1" wide. Someone had cut jute webbing down and it was frayed and sagging. I couldn't find narrower elastic webbing anywhere so I used heavy cotton webbing and stretched it very tightly. It never occurred to me at the time to cut Pirelli down to size! Duh...

Thank you both, extremely h

elpful. Would love to have your help actually IDing the sofa in question, will post pics later today.