In early 1944, Crown introduced the "two-way" track zipper, which featured symmetrical teeth. According to crown advertisements of the time, this particular zip was designed for gun turret applications, with a slider affixed to either side of the barrel of the turret's gun. The symmetrical tooth design allowed for smoother action in both directions, and allowed the zip to go around the curve of the turret. For a photo of one of these zippers in action, see the bottom of the page at this site. The one in that link appears not to be a Crown, however, the same model as the zip on this jacket.
One-directional chevron teeth on zipper at left, two directional (symmetrical) teeth on zipper at right. Spring loaded sliders on both. If you run into a zipper with teeth like the one on the right in a civilian application, it was not produced until after the end of WWII.