Puukko

A puukko (Finnish pronunciation: [ˈpuːkːo]) is a small traditional Finnish general purpose belt knife with a single curved cutting edge, solid hidden tang, and

usually, a flat spine. Military models of puukko were popular in the Russian criminal underworld under the name "Finnish knife" or finka since the 20th century. The modified version were among the models on which the Soviet military knife NR-40 was based and which was informally called "finka".