Peter,

Very fascinating! This is a real find!

Years ago, as an experiment, I made a similar kilt using 3 1/2 yards. I didn't pleate to anything, just keeping the pleats about the same size but with only a single stitch to hold them in place (but a bit lower than this artifact) that would be hidden by my belt. However, since I couldn't document it, I took it apart (which I'm now beginning to regret).

Look forward to any additional information you come up with - and the resulting paper.