In my view, we are talking about two different components. A car as a whole is a mix of numerous components. Even back in the day, just in time inventory was in place and that is why many vendors to any business provided a build date for these components. In this example, the car was actually assembled in the fourth quarter of the production process. However the component piece, the seat belt assembly, would be dated most probably in the second quarter of 69. The independent suppliers all used different methods of date coding their parts. Look at washer bottles, washer bottle pumps, rear axle tubes, door panels, trunk mats, lower control arms, etc. there is no consistent method of date coding the parts. The one thing that is consistent for the vast majority of the car is that these components will be dated approximately 2 weeks to 12 weeks prior to the schedule build date of the car. And never say never as sometimes items were pushed aside and later used outside of the standard production window.