Yes, this is an early bult Camaro assembled in October of 68 so its before the X codes were added to the tags. All I can say is that tag is one of the oddest I've ever seen. It has that notch on the right side, all of the text is offset from where they should be, all of the text is raised up by about half of the stamped fonts height, the interior code is to far to the left, the date code to far to the right, the exterior paint and top color is to far to the left. The rivits have been removed and replaced, so I would say the cowl tag is a replacement. Is there any evidence on the car that it is not a cortez silver car, or the interior is not a black deluxe interior? If you pull the rear seat down, you may see an X code written in yellow crayon on the passenger side of the rear seat support, sometimes its just two dixits like X1, sometimes its more with some derivative of an X code and the cars color like X3RG, for X33 Rally Green. It will be under the edge of the convertible top bag, and if its real (yes people fake those too) it will be under the trim adhesive that holds the bag to the seat support.
Alot of cars were ordered without radios as the dealers could make more money by installing their own radios after the cars were deleivered, but of course there would be no holes in either the fender or quarter panel for an antenna. If the car truely didn't have a radio, or had a rear antenna (an hence an AM radio) from the factory, there will not be a holde drilled in the A piller forward of the passenger door where the antenna cable went from the interior of the car to the space behind the front fender. If theres a hole there, then the car had a radio when it left the factory.