The box makes' it look NOS, but the part doesn't. He might have used and NOS part on his or anothers truck, and clean his up and put it in the box.
I believe that's a true NOS part. Not sure what makes you think it's not.
Here's some pix of my original locks that I cleaned up, reconditioned, and zinc plated. They definitely have the COWLES lettering stamped in, although the passenger side one is pretty faint.
