The third photo shows the tracks I mentioned before, and there are cuttings to show it could be set open in various places - this is normally seen in temples.
One thing no-one has asked is why is the door at Amphipolis so much more
damaged than the rest of the structure and sculpture ... was it locked? and if so, this would be the first evidence of a possible attempt to rob the tomb in Antiquity. Or maybe the slabs were less secure than the rest of the building, so they fell and shattered.