The axle nut that is on your axle is an original style, and the new one that you have is an aftermarket replacement.
Hopefully, you are aware that there are lefthand threaded axles and righthand threaded axles. Originally, they were lefthand on the left (driver) side, and righthand on the right (passenger) side. There are stampings on the threaded end of the axles to indicate which thread you have..."D" for righthand..."S" for lefthand. See pic.
John