The tsuba is usually a round or occasionally squarish guard at the end of the grip of bladed Japanese weapons, like the katana and its various declinations (tachi, wakizashi etc.), tanto, or naginata. They contribute to the control of the arm (the right index of the fighter typically touches the tsuba), and to the protection of the hand.
During the Muromachi period (1333-1573) and the Momoyama period (1573-1603) Tsuba's were more for functionality than for decoration, being made of stronger metals and designs. During the Edo period (1603-1868) there was peace in japan so tsubas became more ornamental and made of less practical metals such as gold.
Tsuba are usually finely decorated, and nowadays are collectors' items. Tsuba were made by whole dynasties of craftsmen, whose only craft was making tsuba. They were usually lavishly decorated. In addition to being collectors items, they were often used as heirlooms, passed from one generation to the next. Japanese families with samurai roots sometimes have their family crest (mon) crafted onto a tsuba. Tsuba can be found in a variety of metals and alloys, including iron, steel, brass, and copper.
These fine tsuba are crafted to replicate some of those from olden times in ancient and more modern Japan.