I have here an actual piece of one of the terminator tanks that rampaged in the office in Terminator 3.  I do not know which one it came from, but it was most likely either T1-8 or T1-7.  Two set photos are included for reference, as well as a photo of it with a pen, which is not included.  Only the little grey terminator piece is included.  In the photos, look at the face, right below the nose.  Each tank had two of these pieces.  I do not know what it is made of.