I've seen a few very much like that from the Archaic site I hunted in NC. I have one about an inch, its the same. I couldn't say for sure I'm not experienced enough. If i had to hazzard a guess, I would say its guilford related. My site was mainly guilfords/sav rivers. I have seen guilfords with basal thinning even that far up the point. Also you have to take into consideration, Cumberlands are rare even in areas that have more chance of having them. I doubt to be honest there are any in NC. Even on the U.S Projectile Point Id site it shows Cumberlands for NC BUT the ones showing are not from NC. So i figure they must me very rare.
I do however know a professional collector in NC, I could ask him if you like? I will Pm you when I get back..
Greg Perino,( god rest his soul) he was the guy that named the Guilford, he was the guy that wrote numberous ID books on Guilfords/lanceolates from NC. He was born in NC I do believe. If it is indeed a Cumberland or Guilford then my friend at the NC museum Cliff will know.
Just trying to help.
Molly.