An important historical Kamakura or possibly earlier period  tsuba, from the Kawagoe History Museum, where it was on exhibit until 2015.  This is what the bushi of the day were wearing.    76mm x 75mm x 1.8mm,  which is an exceedingly thin tsuba.   The kozuka-ana was added much  later.  In fact, the metal is still  slivery shiny metal.  Contrary to popular opinion we can see early screens and hand scrolls. like the Heiji Monogatare,  that show samurai  in the Kamakura period wearing swords with the cutting  edge up that were used by mid level bushi.   Those would accommodate such a tsuba that were used by samurai of the day. This is 1,000 year old working samurai's tsuba, not something from the court or nobility, so it showing its age.  $1,250