  Ultrasonic test block. 
This block of aluminum is stamped "NO 7 ALCOA ULTRASONIC STD. REFERENCE BLOCK A1116".  I'm going to hazard a guess that it's meant for testing ultrasonic inspection systems, which are used to examine critical pipes and welds to locate invisible cracks or voids in the material.  It looks like a solid block, but possibly they have put some kind of defect inside it.  Or maybe it's the reference for non-defective material. 
Source: Ethan Currens 
Contributor: Ethan Currens 
Acquired: 27 December, 2008 
Text Updated: 28 December, 2008 
Price: Anonymous 
Size: 2" 
Purity: 99.9%
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