Re: New vrs old Duncans
I think it would mainly have to do with old used pickups being de-gaussed slightly just by some of these factors....age, being stored next to other pickups, which can change the magnetic strength adversely, and by leaning a guitar against a speaker cab occasionally.
I remember at a clinic, Seymour talked about Andy Summers from the Police wondering why his strat got weaker sounding over time. Apparently, he'd lean it against a metal transformer at the subway station, while waiting to catch the train on his way to rehearsal everyday. It weakened the magnets. After he was famous, he had Seymour rewind his strat pickups, only to find that the sound was stronger, but lacked the sweetness that his strat had, years ago. Seymour also suggested to never lean your guitar against the front of your amp, for that reason, and to store pickups apart from each other....and parallel.