Iron mail or possible lorica hamata fragment.  This fragment however has none of the known characteristics of Roman mail, which doesn't mean it can't be Roman, but rather that there's no reason to believe it is.  The fragment does not appear to have any welded rings.  The one that has a clear rivet hole in it is no different than the others where just the seam is visible, and the tiny size of the rivet makes recognizing them very difficult.  No rivet heads are clear anywhere.  And the fact is that Roman mail isn't alternating riveted/welded rings, it's riveted/solid punched rings.  There are definitely no solid punched rings in the fragment.
 

Mail was originally of Celtic origin, however adapted by the Romans and improved upon.  Instead of continuous rows of rings each "welded" together, there were alternating rows, one being riveted the other not.  This added greater strength and ease of repair to the whole armor.

 
As lorica segmentata came into mainstream use mail or lorica hamata began to be phased out.  It was expensive to make and had some distinct disadvantages for protection over the new plate armor.  By the late 3rd Century however Mail made a comeback and again became the mainstay form or armor.  It is unknown why this occurred, but probably had to do with the fact that Lorica Segmentata was too complicated to make by that later more chaotic period. (1)(2)(3)(4)

-painting by John Warry

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