The car is one of 4,220 or so built in 1969, by Pullman Standard in Butler, PA. Most of the group were built to haul machinery, as evidenced by the two rails running the length of the cars' center line. About 400 of the total group were modified after they were built with the addition of the large fixed bulkheads like my model has, and the machinery rails were filled in with wood. The modified cars were used to haul pipe and most commonly lumber from the Pacific Northwest to points east - This was huge business for railroads in the '70s, before the "Spotted Owl" decision, it was nothing to have 5 trains of various lumber products leave Oregon every day of the week as eastbound traffic.
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