As for Rottnest Island, that was a lovely playground for my son François and me when we used to go sailing on the Zigeuner in 1986. So, at a personal level, this fuzzy drawing is a precious document.
A few years ago, I was surprised to learn that an Australian lady whose maiden name was Sheridan Henty had purchased a house in the neighboring village of Pont-en-Royans. She was a descendant of the Henty pioneers who had reached Western Australia aboard the Caroline. Sheridan showed me a book on her Henty ancestors by Marney Bassett, and that's where I found the fuzzy drawing.