SIZE 37 (10.7 MM) SLATE & SHELL GO STONES JITSUYO GRADE. Condition is New. Shipped with USPS Priority Mail. White stones: bright white clamshell in jitsuyo (standard) grade. Black stones: traditional Nachiguro slate. This set of stones is part of the estate of a long-time friend of mine who was in the Merchant Marine and purchased these stones in Japan more than 35 years ago. Apparently he never used them. They are in their original box and are in mint condition. He was one of those Go players who buy much more Go equipment than they ever could use, saying the items will be a hedge against inflation. (At least that was the excuse he gave his wife!) Few clamshells grow large enough to be cut into stones as thick as these, which vary slightly from 10.4 mm thick to 11.0 mm thick.