Each book has the same grey cover, but the end papers are a pattern from a fabric that was made at the time the book was written, or is somehow relevant to the story.
Saplings has this one -

Which, according to their website is -
"A 1938 fabric by Marion Dorn was chosen for Saplings. It is called 'Aircraft' and shows pairs of stylised pigeons in flight on a background of natural linen. It contains the imagery of aircraft being readied for war yet of birds freely in flight."