The NC 7-pointed "starburst" button at upper left is absolutely a Reproduction. It is solid-cast, not stamped-brass, and none of the Original 7-pointed ones were solid cast.
The other two solid-cast NC starburst buttons in the photo are probably also Reproductions. For 0one thing, you can check their precise diameter with a caliper. The Originals of NC 13 and NC-14 were 22mm.
Compare the ones in the photo (front and back) with the genuine Originals here:
Ridgeway Reference Archive, Civil War buttons
The South Carolina "Palmetto Guards" button appears to be a stamped 2-piece, which is correct for that British-made button. But I've seen some amazing detailed 3-D printed Reproductions of 2-piece buttons that even have the crimp-line on the back. So, when you get to check this group of buttons in real-life, see it the Palmetto Guards is a 2-piece or a solid 1-piece.
Here's a link to front-&-back photos of genuine Original ones:
Ridgeway Civil War Archive Buttons from South Carolina....DRAFT.....
But note, about halfway down that webpage, there are photos of a very well made Reproduction, which has the "weak backmark" we see on the one in the photo you posted. Considering that at least two of the others in the photo are Reproductions, the odds tend to favor the Palmetto Guards button also being a reproduction.
I wonder if the seller, who might be honest but ignorant, has any idea that well-made Reproductions do exist. Please give him the links I included above.... especially the Fake cast Palmetto Guards. There's a lot more at the Ridgeway Relic Archive's "main" section on Fakes, Reproductions, and Replicas:
http://relicman.com/fakes/zfakeAAIndex.htm