Question: Awesome New Bass, But a Mystery

I just bought an Ernie Ball Musicman StingRay5 and it’s awesome. I’m not a very good bass player but what I hear from this guitar makes me wish I were. The mystery is that it has a volume and 4 EQ knobs for a total of 5. Try as I might, I couldn’t find a single reference to any such Ernie Ball. None of the images or the Ernie Ball web site reference it. The serial# is E35313 and according to the serial number data bass, this instrument was manufactured in 2004. It’s in as new condition and everything works perfectly.

Could anyone on the forum give me some information?