Here some samples for Chevrolet from Mc Lellans automotive, the best I could get for the moment. They´re rather small but I think you can see fairly well.

1939: Master De Luxe
http://mclellansautomotive.com/photos/B30484-2.jpg

1940: On the cover SPECIAL DELUXE
http://mclellansautomotive.com/photos/B37368.jpg

Inside the brochure Special De Luxe
http://mclellansautomotive.com/photos/B37368-2.jpg

1949: Fleetline De Luxe in the commercial text and the badge on the car DeLuxe
http://mclellansautomotive.com/photos/H2393.jpg

Browsing through Plymouth and Ford gave a similar picture, the word changes back and forth but mostly it´s De Luxe or at least hard to determine wether it´s a space or not.