Indeed! The episode Miri showed both McCoy and Kirk walking around in an "unzipped" fashionEven the production uniforms had such zippers. Their look changed every so often as W.W. Theiss experimented with placement and cut. Spock's first couple of outings in production even had the zippers on both sides, and his collar breadth changed a few times. I think Theiss settled on one design about mid-season.
http://www.trekcore.com/tos/hd/albums/1x08hd/mirihd285.jpg