Can someone read production week from this serial?
The iPhone 3GS model number is A1303, so I'm guessing that if you're looking at your serial number, it's somewhere with the model number appended to the beginning. To see just your serial number, go to Settings > General > About.

Once you have your serial number, the 3rd character will be production year, the 4th and 5th characters will make up the production week.

For additional info, check out "iPhone Serial Number Secret (Decode Color, Size, Production Year and Week)" on My Digital Life.