If you have fast backs , coupes and convertibles starting a new model how would the serial numbers start . I may be wrong but 01001
could be for the first convertible 02001 for the first coupe and 03001 for the first fastback ???
Not an actual run but to illustrate that the distribution of serial numbers was the next car down the line, the first 5 digits defined the car line (BH29D), even then I'm sure the actual production order may have varied.
