The Borg Wagner example was constructed utilized the various roof hatches found in Athearn's kit. This provides an excellent illustration, but is a non-prototypical model. You'll find round hatches or elongated trough hatches, but not both on a prototype car.

In 1968, Athearn introduces the ACF 5250C 100 Ton Center Flow Hopper. A dozen roadnames are offered in 1968: ACF, Dow Chemical, Dupont, Enjay Plastics, Grace, Great Northern, Gulf Oil, New York Central, Rexall, Shell Oil, Southern Pacific, Union Pacific, plus an Undecorated example. Dealers could buy Athearn stock number 7512, which provided an assortment of one each of the twelve road names. The car's original retail was $2.98 and it was only produced in kit form at its introduction. Athearn's kit provided the modeler's choice of eight round hatches or elongated trough hatch covers for the car's roof. The round hatches would be accurate with the outlets included on the bottom of the model. The hatches would go on a gravity outlet gated car, which is not part of Athearn's design. Part maker Detail Associates offers a set of four straight gravity gates to correct the underframe of the car for use with hatches.

Available online, you'll find a 1994 Rail Model Journal magazine article ACF CF5250 Four-Bay Center Flow Covered Hoppers by Jim Eager. Mr. Eager's story details the prototype's history with info, such as it was built by ACF (American Car & Foundry) between 1964 and 1982. Prototype roof hatch info is provided too, such as an example with eight round hatches would be used for shipping feeds and lighter grains. Six round hatches on the roof would be a 5250 carrying foodstuffs (corn starch, sugar, flour). This is an excellent review of the prototype with notes pretaining to models in HO- and N-scale and recommended reading. You'll find this article and many more complete magazines online at the TrainLife.com website.