The magnetic polarity of pickups can either be South or North. I’ve seen early Fender pickups with both South and North polarity in the same guitar. Early Broadcasters, No-Casters and Telecasters were often made with pickups having different polarities. The early lever switch on the instruments didn’t allow the combination of both pickups and the phasing didn’t matter. The majority of the early Stratocaster pickups had a North polarity and later changed to a South polarity.

Early Gibson humbucking and single coil P-90 pickups are usually South polarity at the adjustable poles. On various Gibson stereo models, the neck pickup is often made North polarity but the pickups are out of phase when used monaurally. Many players want to convert the stereo models by rewiring it and all you need to do is flip the magnet over within the pickup.