Includes road numbers 673224 and 673283.
With the expanding economy and industry after WWI, the necessity for larger coal cars than the typical 50-ton hoppers became apparent. Coal-fired electric plants became omnipresent, and improvements in technology led to a 70-ton, 3-bay hopper, used throughout the 20th Century.
Not long after the 50-ton, 2-bay hoppers were perfected, and with many improvements in railroad track, springs, trucks, and couplers along with ever more powerful steam locomotives, the want for a bigger, more economical hopper to haul the burgeoning coal industry's product led to the development of the 70-ton hopper. Many variations were tried between the early 1920s and to well after WWII, featuring a diverse number of ribs and panels of assorted sizes.