Royal Quiet De Luxe
The Royal Quiet De Luxe family (commonly referred to as "QDL") was manufactured by the Royal Typewriter Company from 1939-1957. The model went through 4 different shell designs, and is one of Royal's most common portables available today. This line is the successor to the Royal De Luxe and Royal Quiet models of typewriters.
The QDL occurs in 5 varieties, with the difference being features. The Quiet De Luxe is the top-of-the-line model with a tabulator. The Aristocrat has a tabulator as well but often lacks some amenities. The Arrow, Companion and Commander models have no tabulator and feature fewer amenities than either above model.
First Generation: Baby KMMs
First Generation QDLs look very much like baby Royal KMMs. They are often found in black crinkle paint, but a few colored ones do exist. These are not to be confused with "candy QDLs' which came in bright, glossy paint.
Second Generation: Dreyfuss QDL
From 1948-49, Royal produced a new generation of QDLs, with a new shell designed by Henry Dreyfuss. "Tombstone" keys were also added. These keys are similar to the ones on the Royal KMG.
Third Generation: '50 and '53 Redesign
In 1950, Royal once again changed the shell of the QDL. In 1953, they redesigned it again, hiding some of the controls on the inside of the hood, and adding a spring loaded ribbon cover, that can be opened by pressing the button on the left side of the front panel. Some QDLs were also equipped with a mainspring tension adjuster.
Candy QDLS are recognisable by their bright, glossy paint colors. They were first introduced in 1955, and ran until 1957. These are not to be confused with later QDLs, as these have regular silver "Royal" nameplates, and the late model ones have red "Royal" nameplates.
Royal QDLs are usually solid machines. However, they are somewhat sensitive to rust, especially the later models. If you experience regular skipping, you probably have a chipped or broken starwheel, or a bent escapement bracket. These are rather prone to escapement issues, so watch out for this when considering a purchase. These machines can also be sensitive to mistreatment in shipping so if you are debating on purchasing a QDL via the internet, talk to the seller about packaging before committing to a purchase.
(All of these are from Richard Polt's site)