The alternator fan shown in the photos at the beginning of this thread is a one-year-only design from a '63 Corvette (and possible other '63 usages); easy to identify due to the 13 blades that are all the same size and shape, each with the little half-moon cutout on the vertical edge. All alternator fans from '64-up had fewer blades, with at least two blades (sometimes more) that had a different size and shape, to reduce/eliminate alternator fan "whine" or "moan" complaints. Somewhere along the line the one in the photo replaced the original fan.