Brianna knew at a glance that we had a “factory bag” and explained that we were in a “full price” store where such a bag “would never be sold.” To further amplify the point, she pointed out the Coach equivalent of the Scarlet Letter, a tell-tale “FS” in the serial number designating “factory style.”
http://www.brandculture.com/blog/2010/06/when-is-a-coach-bag-not-really-a-coach-bag-when-its-from-the-coach-factory-store/