Sharp-Edged 1964 D Nickel?

I'm not really going to bother with a picture of this one... it looks just like a normal nickel, with no odd visual characteristics, other than surprisingly good condition for a coin that's 43 years old... it looks better than some coins I see fresh out of the mint.

But what caught my attention in the drawer was when I was handling it, was how it felt in my hand. On the obverse, the very outside rim of the coin, the border on the face pokes out a little bit, and it feels sharp. Certainly not enough to cut someone, but it does seem rather odd. Perhaps an overly-deep striking?