Typically, this would be a WM-6 Washita. W for Washita, M for mounted, and 6 for the six-inch length. The mounted indicator refers to the stone having been glued into the wood box; this stone has worked itself free over the years, and you can see that the bottom is uneven.
Condition-wise, the box shows some, but not much, shelf wear. But there are no signs of the stone having been used. To me this is NOS, perhaps sold and handled but never used. There are no signs of oil in or on the wood or the stone. The dimensions are, roughly, 5.9 x 1.9 x 1.0
