Unfortunately, I don't have any info, and I havent framed my searchs at the museum website right. I figure I'm safe in calling this a 'mummy board'. the museum info for a three layer coffin refer to the middle board thusly. Much symbolism is present. Three ba-birds are at the top, representing an aspect of what we call 'soul', the immortal aspect: Ba Osirus in the Atef crown is at the center. Several other gods are there, Nephthys, and Horus are among them. Also various Anubis images, (the jackal headed god whose role is attending to the dead), perform necessary functions. Towards the bottom, there's djed pillars and a tyet to help ensure stability and well-being: Three Djed Amulets Djed and Tyet