This would appear to make sense, as the 1946 Car Builders Cyclopedia shows drawings for only three types of box car roofs, all manufactured by Standard Railway Equipment Manufacturing Co. with the following descriptions for the portions between the stamped edge seams: the "Murphy Improved Riveted Roof" with a single raised panel per sheet; the "Murphy Welded Roof" with two raised panels per sheet; and the "Standard Pressed Steel Roof" with flat panels.
Regards, Greg Kennelly
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The last ones I know of were C&NW's War Emergency boxcars, 77416-78248 even numbers, built by P-S in 12/43-1/44.
These cars used existing materials, including the Viking Corrugated roof, from an incomplete order, C&NW 76900-77414 even numbers, built by P-S in 5/42.