Thread: hone ident help please

picked this stone up at an antique store. black with use and pretty dished in the middle. a LOT of laps with the atoma and i get what you see now. its very (very) hard and feels smooth with just a hint of grit. not as smooth as the trans ark i have but pretty damn close. dimensions are roughly 5.75 x 2.0 and 1.25 thick.

any help would be greatly appreciated.
thanks.
-s.