Is my major misdiagnosis that, after all these old tartan pieces I've seen, I'm still thinking of the way modern tartans are woven? It occurred to me after I typed that last post that, if a plaid were woven single-width, then cut in half weftwise, and the two halves joined along one selvage, in order to preserve the tartan pattern, it wouldn't make sense to center the tartan pattern on the loom. Instead, one would want one selvage to occur on the edge of a check and the other to occur right in the middle of a check.

I know I've read all about it before (and seen photographs), but for some reason I got it confused with the way modern kilts are made from double-width fabric.

I still think it's half a plaid or a philabeg. On closer inspection I see two or three red threads running across the top of the piece. I'm assuming the thread at the "C" is where the fabric is hemmed, but the hem is not exactly visible from this side. Is the "IC" intended to be visible when the piece is worn? The way I visualize it, the initials would be on the left apron when worn.