This blueprint shows one of the designs that Whitall Tatum was considering as they were developing their transposition insulator in the mid 1930's. If you look closely at the left side (bottom) of the drawing, you can see a red contour line drawn over the original. This red line appears similar, while clearly not identical, to a CD 200 design. Particularly striking are the similarities in the top 1 1/2" of the Whitall Tatum proposal . It is interesting to see that the influence of the CD 200 transposition survived to such a late date. For a better look at the red-marked area, [id=203685527]