Srbosjek

The knife gained notoriety because it was believed to be used by the Croatian Ustashas during World War II for the killing of Serbs, Romas and Jews in the tens of concentration camps across the Nazi-puppet Independent State of Croatia, most notably the Jasenovac concentration camp.
It is said that in the Jasenovac concentration camp competitions in speedy slaughter were organized by the Ustashas. The winner of one such competition, Petar Brzica slit the throats of 1,300 (or 1360 ) prisoners. However, since recently it is regarded as something that was made up by the Yugoslav communists as there doesn't seem to be any solid evidence of it. It is also mentioned that even if it were true, the number is greatly exaggerated as one would have to kill non stop for 10 hours one person every 45 seconds.
History.
The knife gained notoriety in the former Yugoslavian countries because it was used by the Croatian Ustashas during World War II for the killing of prisoners in the concentration camps of the Nazi-puppet Independent State of Croatia, most notably the Jasenovac concentration camp. 
It is said that in the Jasenovac concentration camp competitions in speedy slaughter were organized by the Ustashas. The winner of one such competition, Petar Brzica slit the throats of 1,300 (or 1360 ) prisoners.
Description.
The upper part of the knife was made of leather, as a sort of a glove, designed to be worn with the thumb going through the hole, so that only the blade protruded from the hand. It was a curved, 12 cm long knife with the edge on its concave side. The knife was fastened to a bowed oval copper plate, while the plate was fastened to a thick leather bangle. The knife was fixed on the glove plate in order to prevent injuries and to prevent taking care of a separate knife in order to improve the work speed.
Such a type of wheat sheaf knife was manufactured prior to and during World War II by German factory Gebrüder Gräfrath from Solingen under the trademark "Gräwiso". 
Gebrüder Gräfrath was taken over in 1961 by Hubertus Solingen.