Oil temperature gauge luminous dial. 
This oil temperature gauge is out of a WWII bomber and it has a luminous dial made with radium paint.  The luminosity has faded, which is known to happen due to the deterioration of the zinc sulfide phosphor.  It is still definitely radioactive (half-life of 1600 years, so it's going to be that way for a long time).  It was donated by Trish Craig of the Environmental Health & Safety department at the University of Illinois at Urbana-Champaign. 
Here's a great article about an object I'd sure like to find and enclose behind a huge amount of lead/ 
 
If you're interested in collecting radioactive things, here is a book I highly recommend. 
 
Source: Trish Craig 
Contributor: Trish Craig 
Acquired: 28 May, 2002 
Text Updated: 11 August, 2007 
Price: Donated 
Size: 3" 
Purity: <1%
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