This is a unique sharpening stone as it is larger than many (3 x 9.7 inch), and is white in color and sort of soft compared to a brown stone for example.  It is permanently mounted into the wood base so I don't know how thick the stone is for sure, but what can be seen  above the wood is 1 inch thickness.   I was told that this stone was used primarily for sharpening razors or razor edge tools. The wood is solid no movement, the stone has a very tight hairline crack near the middle as seen in the photo, but I tested this stone with no problems.  Because it is a softer stone it is easier to re-surface flat after heavy use that could cause uneven wear.  Currently it is reasonable flat comparing it to a straight edge.