You searched for: “casket
casket, gasket
casket (KAS kit) (noun)
A coffin wherein a dead body is placed: The family was amazed at the price of the casket and asked to see other models.
gasket (GAS kit) (noun)
A seal used between matched machine parts or around pipe joints to prevent the escape of gas, fluids, etc.: The rubber gasket on the pipes was important for the safety of the workers.

The old casket appeared to have a rubber gasket around the edge to prevent air from getting into or out of it.