In our current reading assignment (pp. 571 ff), Swann brings photos of the coins of the Order of Malta for la Duchesse to see. Le Duc stumbles over the Order's name : "I said Malta, but I meant Rhodes; in any case it's the same Order of St John of Jerusalem." It's actually all three. The Order was, and still is, a sovereign entity. Here's a link to the wikipedia page on the Order.