Malcolm,
This poster must be close in age as your Johnston poster as it looks to be made of the same size and material even color. This is a waxed covered cardboard type material, it is a very pretty blue & white poster. In the lower left corner it appears to be made in Dayton, Ohio. Don't know how this "Gritic" company fit in with the J.I. Case Plow Works company but I am guessing it was one they bought up along the way??
Joe