Manufacturing accountants refer to what you are talking about as W.I.P. It's Work IN PROGRESS. It's the cost of the parts inventory, and the lead time the parts needed to be ordered, or built, in order to keep a large assembly factory running at a smooth speed. You can bet that one of the "bean counters" knew the exact number of lefthand fork ends were in that barrel. He just could not care less about what serial number was stamped on them.
You cannot build several thousand bicycles "every work day" in one factory without a lot of planning. Remember, this was before we had special apps and laptop computers. The engineers used slide rules, not a CNC program. Planning was with a paper and pencil.
The Schwinn factory was very organized. It just became a bigger job of forecasting the parts needs as the lead time became longer as more bicycle parts companies closed down in the United States and bicycle parts had to be sourced from Europe and Asia.
John