It looks like it doesn't have any defects which is also very rare.
It takes many years to dry such a thick piece of kaya before it's stable enough to use for making a goban.
The wood is also cut so the lines formed by the grain of the wood runs straight up and down the board. You can't just cut up a tree any old way to get this type of pattern.
The wood is probably be Hyuga Kaya which in itself is very rare and valuable.
And the board is made and signed by one of the most famous goban makers in all of Japan, the only one who still uses a samurai sword to do the lacquer dipping.
According to "The Go Player's Almanac 2001",
With the sole exception of Yosida Torayoshi (b. 1927), who signs his board Ichinyo and is the best known maker today, a real samurai sword is no longer used.