I'm no expert on these but to start, the lettering looks sloppy. The color looks off but I suppose that could be the lighting. Here's a link to a discussion on what was supposed to be an original example, with pics for comparison. Copy and paste into your browser:
The colors are wrong, the print is sloppy just like Jecos said. Look at the spacing in the letters (blue and white). Keep in mind that these USA old porcelain companies took much pride in their products. They and GMC would never let something that "sloppy" with the GMC logo go out.