I've seen it on a Brooklands roadster the rear panel wears on the back valance panel. When you removie you have a ring of score marks. I'm guessing the leather covers that.
I thought the same. Will ask him next time I see him.
Paul
1990 4/4 1.6 Ford CVH Sold 2014 +4 2.0 Ford 2005 BMW Z4 2.2 6Cyl Sold