It looks like Siberian aka Chinese Elm to me, I've got two of them down and cut in my yard right now. I have a woods full of Oaks, Ash, Hickory and more black walnut than I would like. I don't think it's Walnut. Everything from the bark, the grain, the leaves, the weight/wetness and the final tell . . . . give it a sniff and see if it faintly resembles Cow P!$$.