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.
Be aware of another code found on these pots, 013446.
It has nothing to do with the date as I've seen the exact same code of pots ranging from 1977 - 1981 strats.
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.
The third pair of digits are definately known to refer to the year.
In this example the pickups were wound by operator #20 in the 23rd week of 1978.
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.
Neck Configuration Codes: 00 = Rosewood fingerboard 01 = Rosewood fingerboard 02 = Maple fingerboard 03 = Maple fingerboard Neck & Body Stamps: WWYD Example: 0304 - Basically the same as the date portion of the nine digit neck stamp although in black ink.
They seem to be found on the bottom of the neck heel, as well as in the neck pocket of the body, or even just stamped on the front under the pickguard on Natural finished guitars.
They are believed to just be some kind of quality check stamps.