This is on the window of a restaurant next to my office building. As used here, this leads me to believe that either the gyro owns the sandwich and the platter, the owner’s name is Gyro, or it is the name of the business. All of those choices are incorrect (because I have eaten there and know it is your typical gyro) or I wouldn’t feel the need to pull out my phone as I was walking by. There should be no apostrophe at all so that you know they are selling more than one gyro (or it would be a VERY short lunch rush). If you missed my article about apostrophes, check it out here and then quit using them to make words plural . . . please!