Historic Three-Color 10x10 Go at Matsumoto Castle

dstone?: Touring an old castle in Matsumoto, I stumbled across what may or may not be a historic Japanese example of multicolor go.

I cannot read what is written next to the board -- I took a photo hoping someone could translate for me.

This could be either an artifact or a re-creation, but it apparently has some historic significance. The 10x10 goban looks quite perfect and new, but the three color stones (black, brown, and white) are very inconsistently sized and shaped.

Translations? Theories?

John F. It's two-colour go - the brown ones are burnt white ones, which are of hamaguri and the black are nachi. They were excavated at the castle. The text is too fuzzy to catch all the details.

(bugcat: For our less Japonically adept readers, hamaguri (蛤) means clam. Wiktionary's article states that it refers specifically to the common orient clam, Meretrix lusoria. I've had no luck, though, in uncovering what John meant by nachi. Jisho gives slate as 石板 with the reading sekiban.)

hnishy: 素焼き here means terracotta, not burnt. Used instead of clam white stones because they were much cheaper. And nachi is nachiguro stones, the usual material for Black stones in Japan.