I'm not expert on these stringed things but my passion for photography may be of benefit here. My Leica M lenses have serial numbers to show year of manufacture. These numbers are released in blocks of round numbers. As they are handmade to order (like the Strat) sometimes customers will be put on a waiting list if they run out of numbers, sometimes not all the allocated numbers are used up. Therefore there is no way of knowing the exact date unless you have the QC certificate.
I have a 90mm lens who's serial number dates it to 1973, but that particular model wasn't introduced until 1974! I think companies release serial numbers in blocks every year and so they aren't in order and can be up to a year out. The person in the factory will just look for a number that hasn't been used up.