According to Fender's information at the link below: "1982 saw the introduction of the U.S. Vintage Series instruments and “V”-prefix serial numbers. The only way to definitively date U.S. instruments with “V”-prefix serial numbers is to remove the neck and check the butt end of the neck heel for a production date, which may be stamped or written there."
brianeharmonjr is correct - until the big revamp in August 2012 the serial numbers on the American Vintage models were essentially random going back to their introduction in 1982. They were done the way they were in Leo's day - dump the numbered neck plates into a parts bin, and take them out as needed for assembly work.
Now they did make a change with the new models - the serial numbers still start with a "V" but the first 2 digits are now the year, then followed by a 6-digit serial number. So the 2012 models were "V12xxxxxx", a 2015 would have a "V15xxxxxx", etc. (not sure when the AV's "change over"; the rest of USA production "changes over" roughly February/March of the year). That is across the entire lineup; previously the '52 Tele only had a number stamped on the bridge plate (no "V" like the other models), now it also follows the new convention.
That being said the '57 Strat was discontinued when the new lineup came out in August 2012 - the Strat models went from the '57 and the '62 to 3 models - the '56, the '59, and the '65.