James,
you guessed correctly, it its the narrow band that runs horizontally across. In the original MB-Tex lining that strip was created by embossing (I believe) but when you buy a leather cover now most vendors recreate that look by by actually sowing in a strip of padded piping.
Call Jack (or Genie Sanchez) at GAHH and ask whether they will sell you bare panels and the pre-cut, pre-sown leather (or MB-Tex) covers separately.
