Seymourizer II, which evolved into the Distortion neck, SH-6n and MJ wound it. Masta' C can probably give you a range of years.
https://www.seymourduncan.com/blog/faqs/labels-built-before-2002
Cool. It was in the bridge position of a Flying V I bought. It was WAAAAAYYY too bright so neck pickup makes sense. Pickup reads 13.0 Kohms, BTW.