I remember seeing a similar advertisement when I was at Leith Nautical for a post on Tristan Da Cunha. As I remember it you would also have been responsible for the postal service on the island (sorting the mail and franking presumably for pick up and delivery by ship.)
I hadn't got my ticket then or I might have been tempted but I suspect lack of experience would have set me back. Good thing to have on your CV though, 'Post Master General of Tristan Da Cunha.'