ekeup
0
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 - Dec 2, 2011
 
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Those look like something I've seen before. I just can remember specifically what they are.
Maybe some type of "master" discs for duplication? Like a CD master?
Has nothing to do with duplication.
	
	
	
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	Those look like something I've seen before. I just can remember specifically what they are.
Maybe some type of "master" discs for duplication? Like a CD master?
	
 
	Current item....
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Looks like some sort of older data storage unit.
an abrasive disc for polishing?
They are used to ( trying ) to detect black holes in space
Plug plates used for spectral analysis of stars
Like this:
http://sdss3.files.wordpress.com/2010/11/plugplates.jpg