Unidentified Natural Oilstone Sharpening Stone
A pale grey/green oil stone or sharpening stone.
There are a variety of paler spots visible on the surfaces under a magnifying glass but little else to aid identification.
This stone measures 8 inches (203mm) by 2" (51mm) by 3/4" (19mm) overall.
It weighs 14 ounces or 396g.
The top surface is reasonably flat and smooth with a few shallow depressions, please see images.
Some chips to the edges with a larger one to one bottom corner.
Housed in a craftsman made oak box that measures 83/4" by 23/4" by 15/16" overall.