Late 70's Strats have the serial number on the headstock below 'Fender'.
The number will have an 'S' prefix (possibly an 'E', read below) followed by a six digit number.
Pickup Codes: OOWWYY Example: 202378 - It is believed the first two digits are an operator designation for the person operating the pickup winder, this according to Abigail Ybarra herself.
The second pair of digits are the week, but I have seen one example where the second digits were 72.
Pot Codes: MMMYYWW Example: 1377818 - In 1977 found on the side of the pots, moved to the bottom (and unfortunately sometimes covered with solder) in 1978.
Large Letter Stamps: Not 100% sure what these mean, but I have a theory they were used to grade a body prior to recieving a finish. I have seen four A stamps on Natural finished bodies, and a trans-red with an A stamp. I have also seen a D, along with an A on a Sunburst body.
This is just a theory, but if only A's were put on Natural finished guitars as an example, it could help determine if a guitar is refinished.
First four digits are paired up, 09 is the model number for the Stratocaster, and 00 is the neck configuration, in his case a fretted Maple neck with a Rosewood fingerboard. 38 is the week, 9 stands for the year, 1979, and 3 is the day of the week, which is Wednesday.
The '*' represents a middle digit that is either an 'X', a '-' or something that resembles a '1/2' or '1/4' fraction.
The first digit is supposed to reflect the year of manufacture, but there are major overlaps in this regard, and . An important thing to look for are the matching serial number stickers in the neck pocket and on the pickguard.