I have some HNK $5 SN#'s that are lower (not as low as that one) but much lower than other prefixes too. I think the SN shift up and down is a variation we see from time to time. Not common, but whether its uncommon enough to command much of a premium is in the buyer's hands. Like "missing circles" on the $10's (which are not too common but not really "rare") there are thin and large borders on the fives too, but whether there's the demand is another story.