NavList:

Luc, you wrote:
"I see it the other way - as an alcove dug into the beam, rather than a case hanging from it. Perhaps the 'A' shape and the placement of the other octant next to it suggest that it is the storage space for the octant on the floor?"

Nah, that's a perceptual illusion --like when craters in photos of the Moon apper to be domes. You can tell by the lighting as well as the perspective, which the artist is clearly rendering as realistically as possible, that that's a case and not an alcove or niche.

I don't know what is inside the case, but I suspect it is a small sheep.

Frank Reed