What the heck exactly is a PROMO car?

I bought my 71 cuda a few years back and was told it was a "promo" car. Ive found a few articles and threads but none that really explain if being a "promo" car is a good thing , bad thing, or just no big deal. I also found a thread from 2017 mentioning MY vin 100126 as one of three known 340 promo cars with my options. Ac, yellow, and automatic trans.. Maybe someone can give me a quick lesson. sure appreciate it.

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