Here's a question for any pilots who interact with Seattle ARTCC (ZSE) or Oakland ARTCC (ZOA). Attached are maps of the low-altitude sector boundaries of ZSE as of July 14, 1999 (by courtesy of Willamette Aviation) and of ZOA as of March 10, 1988 (by courtesy of the FAA). Does anyone know where I can find the equivalent maps, with the boundaries that were in effect as of November 24, 1971? Or alternatively, any FAA document that affirms that the sector boundaries were the same in 1971 as shown in these maps? Many thanks.