Shibuichi Tsuba with Minogame and Bamboo Motif. Besides the Minogame being a symbol of longevity it is said to be one of the inhabitants of mount Horai an island paradise. The Bamboo and the Kami together allude to this Mythical paradise. The sweeping lines behind the Turtle are  it's tail.  This is not necessarily hair. It could be symbolic of seaweed that has attached over a great span of time.  
While the Patina is very brassy in color the plate is composed only of Silver and Copper. The composition is not precise since many different types of Shibuichi scraps were used to make the ingot it was forged from. So the exact proportions are unknown. It is likely to contain between 40 and 70 percent Silver. The Yellow color is known as Kabure (rash) and is not the normal ideal color for shibuichi, but I like how it works here so I left it as is.