This plug is mainly used in Italy. Two versions exist, 10A and 16A. (The ungrounded plug is type C) The 10A plug has the same dimensions as the Euro-plug and Schuko, with 4 mm pin diameter. (Shown in the drawing below)
The 16A plug is larger with thicker and wider spaced pins. 16A outlets also accept 10A plugs.

In Italy special versions of the Schuko socket outlet can be found that also accept the Italian 10A and sometimes 16A plugs.