PART IV. Die Errors:

Die Deterioration / Deformation: 

Well-defined rings on Euro coins

Raised rings with varying degrees of completeness are often found on zinc cents just inside the design rim, and these are universally recognized as manifestations of die deterioration. Die deformation rings are sometimes found on other U.S. denominations. At first the rings  on this Euro coin seem too complete, too sharply defined, too uniform, too narrow, and display too high a relief to represent die deformation. The fact that an identical ring is present on both faces seems to further undermine the die deterioration scenario. Inside the rings there are no signs of conventional die deterioration (e.g., radial flow lines; orange peel texture).

Still, there seems to be no other explanation other than die deterioration.  The design continues on top of the ring, which would be consistent with die deterioration.  Similar rings have been found in coins from Thailand.

Obverse and reverse of the ringed and normal version 10 cent Italian Euro coin.

Close-up of the southwest quadrant of the reverse face of the ringed Euro coin.

Close-up of the southwest quadrant of the reverse face of the normal coin.