This is Highland Stoneware car! Have a closer look and you'll see that the car is covered with pieces of broken pottery.
I checked Titles & Forms of Address yesterday about peerages, addressing Peers in general and Marquesses in particular. (Not that I shall be addressing any of them, but if I want to write about them, I'd like to get it somewhere close to correct.) Here's what I found. Marquis is the French spelling of the English word, and the Scots usually prefer that spelling though it is up to the incumbent to state which he prefers. The Irish form is usually Marquess.
The titles are usually territorial, as in The Marquess of Londonderry, whose family name is Vane-Tempest-Stewart. (The ancestors were noted in the north-east of England for coal mining, developing Seaham Harbour and once owned Wynyard Park in County Durham. In 1987 they sold it to Sir John Hall of Metrocentre fame, and as of 2002 it was up for sale again for £8 million.) The eldest son is known by his courtesy title of Viscount Castlereagh.
Sometimes the titles are family names, as in The Marquess Conyngham, The Marquess Camden or The Marquess Douro - though the present incumbent of the last title prefers to to use the prefix of, as in The Marquess of Douro.
Younger sons of dukes are addressed as Lord John (Christian name) Smith (family name). A Marquess is addressed as Lord Camden, or Lord Conyngham, or Lord Douro. The Earl of Monkseaton would be addressed as Lord Monkseaton, and Baron Westly, family name Whitworth, as Lord Westly. So...my characters should be able to tell when they address the younger son of a Duke and when they speak to a lower ranking peer.
But I think I need to check and see how younger sons of Marquesses, Earls, Viscounts and Barons are addressed. I suspect the youngers sons and daughters use the family name - Lady Diana Spencer is an example, but if a Duke's daughter is called Lady Jane Watson, how will the difference in rank known?