First 1967 383 installed in a Barracuda

A56 said
According to VIN #'s, several 67' Barracuda 383 Formula 'S' cars were
built in the November production at Plymouth.

How does one determine production date based on the VIN, or is this saying they know of specific VINs with specific build dates?
And were these cars sold to the public?

Not asking you specifically, just asking.