What's even stranger is that PCGS was not even around in 1964, and I think it is a bristle from a brush rather than a "staple." Nicely centered and on the obverse, as well as being squarely on the bust. Waited a long time to get one like this. Thank you @Fred Weinberg
very cool error. I've been wanting to add a Kennedy error to my collection, but they are mad expensive. I'm sure this one was too!
It's hard to tell, is the staple retained in the coin? That's pretty cool! And, I do think it is a staple, not a brush bristle. Brush bristles don't usually have that shape - they are more often straight.