This third photo from the 1951 catalog is difficult to place on the layout, but I believe this oil derrick area is located toward the left end of the layout.  It is interesting to note that the trains at the top of the image are clearly Gilbert HO.  On the right side, you can see a slope back tender which was a feature included only on the Pennsylvania 0-6-0 switcher which was not marketed in S gauge until 1957, but was introduced to the HO line as number 155 in 1949.  On the left is what appears to be a 151 HO Hudson, bearing a 4 digit prototype number 5318, about to enter three HO girder bridges.  It also appears to be missing its leading truck.    HO trains were not included in the 1951 catalog and in fact were not produced between 1951 and 1954.