Monark introduced the Coupe DeVille before they were bought by Huffy (end of 1957 if memory serves) but as others have stated this is the Huffy-built version. First one I've ever seen and it's amazing that it's survived complete and in decent shape. It's probably not tremendously valuable, but you won't have to worry about everybody else having one. There probably weren't many built to start with, and the number still surviving is anyone's guess, but very few.
And when @Freqman1
says it isn't very valuable, he just means it isn't worth 4 or 5 figures, like most of his bikes are. Take it to a show and park it beside a line of Phantoms, and see which gets the most looks. The experts will be nit-picking every detail on the Phantoms, but on this one they'll just be scratching their heads.