This model began as a Rail Shop ACF 3000cf carbon black hopper. The prototypes were built between 1933 and 1949. In the 1960s many of the cars were enlarged to 4000cf by raising the roof 28 inches. The modification also included replacing the staff handbrake with a horizontal brake mechanism, partial removal of the A end side ladder and replacement of the wooden running boards.

The kit was built per the instructions with a few exceptions. To replicate the taller prototype, the sides were cut along the base of the riveted zee at the top of the side stakes. New side extensions were built from styrene sheet and strip. Likewise the ends were cut and extensions were added. Brake gear components were replaced with Moloco parts, other than the brake cylinder/lever part, which is from the kit. The trucks were replaced with some from a Proto2000 gondola kit. A placard was added to each side to display the Columbian Carbon logo.