Wartime production Jens risom armchair, parachute straps  

I had the good fortune to find this a few days ago. It is Birch, which I understand was done due to wartime restrictions. Did they stop the birch directly when the war ended? The armrests on this one are wider than the legs. That sets it apart from what I see on the web. When did they thin out? The original strapping in wartime would have been made from rejected parachute straps. Mine look like they have probably been replaced, possibly just remounted. how can I identify the correct straps for this? Width, thickness,....
The top part can be adjusted for tilt. The chair is noisy and messy. I am completely enamored.