Yes, a letter in the first position means something. Depending on the letter, it could mean: dealer demo, lease car, sold in Canada, sold for export, outside modification such as sunroof, sales bank, package car like a Superbird, Hurst 300, TAs and AARs, special order, and other meanings. The meaning of the letter can change from year to year. There are few hard and fast rules regarding specialty VONs.

I have seen speculation that the third digit of a three digit specialty VON (typically a 700*** or above VON) may have something to do with routing and sales.