The Fender USA “S9” serial numbers covers the years 1978 to 1982 and not (as you might expect) just 1979. The only way to date them accurately is to take them apart. This bass was made in 1981
(has the date sticker in the neck pocket along with the serial number sticker which matches the number on the headstock) and the pots also date to this year.
The pots have been changed at some stage with good quality replacements, but the originals have been kept and are included.