It was the basic design given to the pickup when first designed by Seth Lover in the mid 50s. Originally the pickup was designed without adjustable pole pieces and a row of six pole pieces were added as a “selling point” to enhance sales since the P-90 had adjustable pole pieces.

Traditionally under a cover, the concealed studs are used to conduct the magnetic field to the strings. Gibson traditionally used one row of adjustment screws to give minimal balance to the strings. The stud side has a stronger magnetic field than the adjustable side. With adjustable pole pieces, a small amount of magnetic field is directed out of the bottom of the pickup.