Japanese Relic

I received this item after my grandfather passed away in 1992 because no one else in the family wanted it. I was told that after defeating the Japanese, he acquired this item that had been hidden in a Okinawan cave. I refer to the figure as Buddha although I've been told that he's actually a god of prosperity (or something of that nature). A Japanese history professor told me that it is probably several hundred years old.

The throne part is made of wood and my impression is that it is not as old as figure itself. I'm not sure what the figure is made of but it seems to be some sort of mineral as it's quite heavy and solid. On the throne, it is 23"h x 9"w. The figures itself is 7"h x 4.5"w.

The figure is not in great condition, presumably due to the fierce battle fought on Okinawa. The left foot is broken (and missing), right foot appears to have been reattached. The color is faded to worn away, particularly on the lower body.