I think each brand probably have different sharpening angle, for example Benchmade is 30-35 deg inclusive, Buck is 13-16 per side, etc. You probably could find these info on their websites.
Since there is always variation, even on a factory edge, one of the ways to find out whether you are sharpening at the same angle from the factory edge is probably to use a black marker to mask the edge and see whether you are sharpening at the corresponding angle and apex correctly.