Gaspare,
Though I've not compared every ring in existence, my study of this particular panel reveals these flaws time and again. Here are 2 others in comparison to judge for yourself. Though minute, you can still make out several of the flaws that I speak of, which consist of left over material. Those specks and deformities are in the actual master cast.

FR2a (Custom).jpg (84.63 KB, 370 downloads)