Pictures please Terry.
My similar one-long-term owner from new XK140MC OTS (after buying car from original owner in c1958) received a paint/trim colour change at some stage, but still came with its original Biscuit Coloured heavily-grained PVC Tonneau Cover, that I suspected was its original Duranide cover, but I struggled with little solid evidence against popular comment/belief and 100.0 point cars using Mohair (type) material. Thus I was/had-to-be somewhat cautious with the wording I used when writing-up/detailing Plate 11-a1 in JAGUAR XK140 EXPLORED.
It would be great if I could tighten up on this XK140 applicable wording/detail, and from what you say the use of DURANIDE material looks to have been introduced from late XK120, rather than me suggesting maybe only from very early XK140, and on into XK150 (so fully covers XK140 period at least.
It would be great to establish something definitive for all XK140, and leave the demarcation debate with exactly when with late XK120, and indeed whether to end of XK150 or not, with E-types not relevant of course.
Roger