This early fuchi has yamagane foil applied over a very thin copper backing.  Decoration is in the form of 5 different punched designs including flowers, quatrofoil inome, and turtle-shell mosaics.  Yamagane is dark olive brown in color, but black lacquer coating the fuchi is still largely preserved, and gives the piece a darker tone.   The weld is still seen clearly on the mune side of the fuchi.  Overall wall thickness is only 1mm.  Foiling was a popular technique during the sengoku period as a cost-reducing measure, whereby the amount of more expensive alloy was reduced by foiling a cheap copper core. 

Mid - Late Muromachi  15th -16th c.

Similar Item:  Uchigatana Koshirae, Tokyo National Museum, 1987.  Koshirae 14, pg. 49.