VIN #'s

Curious what people know about the Sub 2000-2003 VIN #'s. Why do some start with 1, and others 3?? They do not seem to corrispond with model years? Are ther different manufacturing plants?? these are all generally K1500's.

thanks for the info in advance

jeff

1 - assembled in USA
3 - assembled in Mexico ( wouldn't worry about this. I'm on my second Sub from Mexico and don't have assembly related complaints. )