I went over these briefly yesterday so I'm certain I'm missing important details. The earliest seems mostly just to describe stacked singles but tries to differentiate what makes his approach unique from earlier attempts (otherwise why grant a new patent?): https://www.google.com/patents/US5668520 I noticed this describes the shielding he uses a bit to isolate the upper and lower coils. Even my oldest set has this shielding. The first time I took the covers off of his pickups, this is what I noticed: https://www.google.com/patents/US6103966 This one I didn't get after a quick read through. I'm kind of hoping someone can give me some better into insight as to what the point of this patent is. https://www.google.com/patents/US7022909 Magnetic flux concentrator! This patent describes increasing the efficiency of the pickup. I suspect is a big factor in what makes his Extra Vintage Astound work the way it does. https://www.google.ch/patents/US8791351 I kind of wish he went into a bit more detail of the design of his pickups and what makes them unique on his own site the way Bill Lawrence does and the way the guy who makes Zexcoils does. As it is, I hate his marketing but love his pickups. It's not voodoo. It's part science, part experience, and a bit of an art as well.