Most people don't...try to figure out the scale ratios that is. The only place where you expect a consistent scale is with the high-end products specifically billed as (or implied to be) scale-proportioned. Starter-set trains (especially from the postwar period)...weren't.
When these "traditional size" cars were developed in the mid-20th century, they were developed as toys, and there wasn't any thought given to keeping a consistent scale throughout the lineup, much less co-ordinating with other manufacturers. The only numbers you'll see here are made-up ratios, since a good number of postwar-peroid models aren't even based upon specific prototypes where you could compare blueprints to derive a specific ratio of reduction.
Besides, during that period, real freight trains had highly inconsistent rooflines, providing even less incentive for toy train companies to do so. In contrast, HO and N scales were created with scale fidelity in mind, and have no "baggage" in the form of a large installed base of product built with no specific scale in mind.
---PCJ
