Just got a new P-bass pickup (Fender Original Vintage #0992046000 - alnico 5, "vintage 62" design) and in the process of messing around with it I offered up an allan key to the pole pieces to see how heavily magnetised they were. It looks to me like the 4 poles in the D+G section of the pickup are more heavily magnetised compared to the 4 poles in the E+A section. (the level of magnetisation appears the same within each section though) Has anyone else seen this? I've never seen this mentioned before, but it looks like a way of balancing the different string output. I fitted the pickup today and it works perfectly and is nicely balanced across the strings, so that difference appears intentional.