Lam, this is a tricky subject to discuss without the living example in front of us. But speaking in general terms we have words in koi that trick us. here is one of my favorite word riddles:
all tategoi are unfinished fish. But not all unfinished fish are tategoi!
Think about that.
The most common yet most misunderstood concept in nishikigoi is the tategoi. Often referred to as 'future fish', 'potential fish' or 'unfinished fish', Tategoi is an enigma in the hobby. It really shouldn't be. A tategoi is a potential fish or a fish that shows traits that could become a desirable prototype higher class fish if the traits continue to develop. This is not centered on finishing unfinished color.
A koi breeder/ farmer will keep all fish that show certain traits. And first cull and then sell off the drop outs. But no tateshita is a tategoi. And it is difficult to watch and read some posts that review tateshita and talk about the future of the fish. Certainly this fish we are discussing now is not Tateshita!!! It is a high class fish. I am just suggesting the traits that are there are nearing a conclusion. It is more unfinished at the this point than tategoi. I cringe and worry that the owner of this fish might be fuming and taking these comments personally. They should not! First this is only my opinion. And second, ALL koi have a window in time. More than a few years ago I had the privilege to see two very famous fish in their home settings - the inazuma showa and one of the All Japan GC sankes of great fame. They had reached their peak the year of the show and when I got to see each one they were past that peak. These were once the best fish on the planet earth for a time. When I saw them , they were no longer of that description or title. This is koi.
I suspect that this showa will grow, the sumi will finish and it will be an incredible show fish. I can say that because basically this fish is now what it will be in the future, VERY well patterned and brightly colored. Very little guess work left in this fish. It is what it is. I can see it's peak coming, can't you? It's a simple extrapolation.
I'm getting long winded now, but just to finish up the concept ( pun intended),
the key to most show fish is the concept of jitai. In 'good old boy' talk it means, when a fish is right--- it's right. In JR talk this means that ALL FISH are blessed and also limited by the type of skin they have. This fundamental factor controls the color development, the rate of finish, and the look and the lasting power of the color cells. And this type of skin I refer to is typically found on a certain type of bone structure due to selective breeding.
In the end, it is fun to gamble on fish. And understanding about skin type is one way to reduce the odds. determining sex and the stage of development a fish is in at certain age and size is another. We should NEVER demerit and discount a fish that is finishing early in life, especially male fish. They can be quite beautiful and a satisfying experience to own. But we should not dream too hard on fish which are very finished at a young age. Instead, enjoy them for what they are and if they are that one in ten thousand fish that break thru the odds, enjoy winning the lottery!

JR