Utsuri, as a consumer as well as a judge, I only hope that domestics will get to the level of Japanese stock in my life time!
And not to worry about my dollar, I have another one in a sock in my dresser drawer!
OK, first things first. If judged properly, koi are judged according to age and sex. So what makes for a winning baby is not the same as what wins as an adult or a jumbo koi as a GC. Secondly, GC judging is a judging of the best fish in THAT particular show. So the definition of GC is an ideal as many shows in the USA can't or don't field a Japanese level GC.
Understanding this, a GC is typically a female ( 99% of the time) because when judging adult fish, the males don't pack the body that the females do. And almost by definition, these large fish are of a full adult age ,meaning they are past puberty and in the range of at least 4 and usually 6-8 years of age. This means that the fish is large and robust. Very hard to find a male that can compete with the female body at that point. Secondly, females tend to develop different skin as they meet up with their maximum female hormones. This generally makes patterns stand out and the 'Jitai' just right.
SO- female of 28-32 inches, age 5-9 and skin that gives the color ( of high quality dimension) and pattern ( least important believe it or not) that high class look. This is a general description of a GC.
To get that 28-32 right body you require a great bone structure. That is part genetics and part environmental impact on the development over the previous 5 years.
As mentioned, on top of that bone chassis you need the right quality skin.
The skin also has to be brought along so that it develops correctly. This is perhaps where those who think the owner isn't 'judged' along with his fish, need to reconsider. For instance, an owner can bring an average good grade fish up to compete with a super grade but poorly cared for better fish. A breeder will still pick the better genetics. But an amateur judge will often pick the lesser but better conditioned fish. Hopefully this sliding scale of quality vs conditioning will be well understood by the amateur judge and a strong rational can be pointed to. But I digress--------
JR