Ask your LFS where they got the fish from--that will help you track down the breeder. Each breeder may and typically do have their own grading system.
Keep in mind that grading is subjective. The only system with even a slight chance of being reputable is the one used for Picassos which only accounts for the white bars touching/joining or not.
If we were to even attempt to grade your clown, we'd need photos of both sides as symmetry plays a part -- this is assuming you want us to get into the nuances of grading, at the risk of pointing out defects you may not want to know about (your typical "do you want a pet dog or a show dog?").