Antique Japanese Kozuka and Kogatana
Kozuka is the handle portion of a samurai utility knife. The symbols in red to the left are the kanji for "kozuka".
Samurai swords were often equipped with small utility knives inserted into the side of the scabbard. These knives were made from two parts, the handle and a separate blade. The blade portion is called the kogatana and the handle is called a kozuka. Common materials for kozuka construction were mixes of iron, copper, gold and silver (shakudo and shibuichi were popular alloys used in kozuka, kogai and tsuba).
Kozuka were almost always of the same size and length (roughly 9.8 centimeters in length and 1.5 centimeters in width). The kogatana blades were honed only on one side (as are most Japanese knives) with the other side being completely flat.
Today both kozuka and kogatana are popular collectibles for the nihonto (Japanese sword) and tosogu (sword parts) crowd. Kogatana in great shape are somewhat rare these days but they do show up from time to time. Signed kogatana are even harder to come by.