What name is given to a casket where the rim, crown, and pies are formed as one unit and opens as one piece?

The term that best describes a casket where the rim, crown, and pies are formed as one unit and opens as a single piece is "Perfection Full Couch." This type of casket design provides a seamless appearance and is traditionally used to offer a more elegant and cohesive look at the deceased.

In a Perfection Full Couch casket, the entire lid opens at once, allowing for a full view of the deceased, hence the term "full couch." The unity of design is significant for both aesthetics and structural integrity, contributing to a dignified presentation during memorial services. This construction differs from other types of caskets that might have modular components or separate lids, which would not provide the same visual continuity.

Other options, although they may refer to casket designs, do not accurately describe the specific features of a casket that opens as a single piece with all components formed together.