It looks like a regular Egyptian sarcophagus, except it has the head of a cat. It's golden and has many symbols on it that resemble hieroglyphics. There are two green gems shown on top of the cat head, in the form of headgear. The inside has no markings, but just plain golden walls.
This may have originally been a sarcophagus for a cat. Egyptians did mummify cats, because they were sacred animals, and used as offerings for the goddess Bastet.