Actually, the disks I used to see that size (5 or 6 foot diameter) were used by a couple of my fellow DEC Field Engineers as picnic table tops when the drives were decommissioned. Aluminum makes a nice weatherproof table top. (They must've come from KL10s or KA10s or KI10s, though. I've never seen anything that large on minis...) Don't know how the iron oxide does though. Perhaps they were painted when used.