IMHO the hint of a recessed hinge-pin in the pictures is that the forearm iron is worn bright across the bottom where carried and is still darker on the side where the hand doesn't touch it. Many things could cause the idea of the damascus pattern to the barrels -- pattern from the gun case interior in the gun oil on the barrels, pixilation of the photograph, etc.
As to the other comment, Philadelphia Arms Co. did offer Damascus barrels on C-Grade and higher in their 1905 catalogue, but none but Krupp barrels have surfaced so far. Also, a Philadelphia Arms Co. forearm would look just like a Parker Bros. forearm --
E-Grade on left, C-Grade on right, not at all like the XE-Grade Ansley H. Fox forearm in the Aldo Leopold picture.