The name DeVille was dropped after 2005. But as 1993 SLE mentioned, there are three different 'trim levels' or 'option packages' available for the DTS. Most rental car agencies that offer a DTS only purchase a DTS I that is pretty basic. When you get into the II and III you'll see a lot more toys. For example, heated washer fluid wasn't offered until you reached at least the DTS II. You won't see the I, II or III anywhere on the badges though. I can't find my sales brochure, but if you drop by a dealer it'* very well documented.
The same as the SE, SLE, GXP, you'll see columns of options listed as DTS I, DTS II and DTS III.
Because your car is a 2003, it may or may not be defined the same way.
StingRay Bike w/cards in the spokes, Weeeeeee!