SGI: Hardware

Please help indentify these are cover or sled

Hi, I am researching whether these are simply spacer or cover, or indeed a empty sled without hdd attached?

In this picture, the bottom one appears a hdd, what about above five?

Thanks

http://hardware.majix.org/computers/sgi.origin/images/o200.02.big.jpg
:Indigo: :O2: :Octane: :Octane:
The other five are blank cover plates. They have a backside made of sheet metal to provide shielding inside the O200 case
:Crimson: :PI: :Indigo: :O2: :Indy: :Indigo2: :Indigo2IMP: