For your consideration, here is a Vintage Washington State WPPSS I Visited WNP-3, WNP-5 Pinback Button, Pin, from the old Washington Public Power Supply System.  The WNP-3 and WNP-5 refer to the defunct Washington Nuclear Projects 3 and 5 at Satsop, Washington.  It has some wear on it.  There is a little tarnish on the back.  The button has a diameter of 2 1/2 inches.  Item pictured is the actual item up for sale and comes from a non-smoking household.  (431.316v-.4px2)