It's possible you're encountering one of the following:
* A custom or aftermarket modification: Someone may have customized a DeVille and given it that name. This could involve unique paint, interior, or added features.
* A regional dealer-specific package: In rare instances, a dealership might have created its own package and marketed it locally using a name like "Southwest Edition." This would not be a factory-offered option.
* Misremembering or miscommunication: The name might be slightly inaccurate.
To know more about a specific vehicle claimed to be a "Cadillac DeVille Southwest Edition," you'd need more information, such as the year of the car, photos, or details about its features.
