It could also be a cut in the coin, believe it or not. Knife cuts don't remove metal, rather they raise it up next to the cut. When the coin is then circulated for a long time, the raised part wears and covers up the cut.
looks like a feeder finger die gouge to me, BUT it is normally on the reverse, not the obverse because the feeder finger scrapes across the anvil die when it's out of adjustment and not the hammer die. which is "up" on the feeding between the dies could it be a die gouge still? Yes, not from feeder fingers, but it could be from something else, could be a lot of things. if it was a die gouge, there should be other examples of it out there besides just this one which leads me to believe it is a cut of displaced metal that was then pushed back over the cut..... I don't find anything similar on any image searches I did for die gouges on 1951 Ds and you'd think if it were a die gouge others would have turned up in the last 70 years to compare it to of that die pair. all in all, it's the more likely cause of the raised metal, a cut to the surface that was then pushed back down during circulation covering the cut over with a raised area of metal. I am in agreement with messydesk as the more likely scenario.
