This is from the website of the desperately-trying-to-launch Manchester Food Co-op:
How do you know if your milk is bottled locally?
Look for the code.
Each dairy product has a number code on the package. The first two numbers of the code tell you what state the milk is processed in and the rest of the code indicates the processing plant.
The codes for New England are: Connecticut 09; New Hampshire 33; Massachusetts 25; Rhode Island 44; Vermont 50; Maine 23. If a code starts with these numbers, you know the product was bottled right here in New England.
To learn where your milk is bottled, please visitwww.whereismymilkfrom.com
Jane's Lessons Learned 
I had to check this out. Since my Walmart Milk had a code of 07:14 I went to http://www.whereismymilkfrom.com/allDairies.php and guess what? There is no state with the code of 07!