It's 2-1/2" high and has the letters - MI&S Co. embossed on the side.
Only thing I can find on MI&S Co. is the Missouri, Inland & Southern Railway Co., but what would a piece of their track be doing in North Carolina?!?!?!
About the only RR I know of that went thru Sunbury was the Suffolk & Carolina Rwy, which I think was narrow-gauge. Here's a map showing the S&C route, Sunbury is just below Corapeake in the center of the map in Gates County:
The S&C became the Virginia & Carolina Coast Railroad in 1906, which was then absorbed into the Norfolk & Southern, which was then re-organized as the Norfolk Southern Railroad.
I figure it must be at least 100 years old.
Anyway, I was thinking about making some bookends out of a couple of pieces of the rail, maybe even a doorstop with the leftover

