I would not buy something labeled "unturned" half blacks. Frankly I dont believe they exist.
A fish expresses or it doesnt. By the time it is nickle size, that's what its gonna look like.
This is actually a new phenomenon. When I was doing half blacks 7-8 years ago, they either expressed, or didnt and you'd be laughed outta town for this idea they would magically turn color. I have never before heard of "unturned" half blacks or seen a fish that doesnt express suddly change color. If its bigger than a dime, that's what its gonna look like. I'd bet more money on that, then I would waste money hoping to hit the fish lotto. I guess it could happen, but I wouldnt play those odds.
Either splurge on half-blacks or buy silvers. There is no point in paying mark up for a silver in the hope you one day wake up to a half black. The only thing an unexpressing half black is good for is attempting to get half blacks in a second generation for someone with time money gear knowlege and experience and desire enough to devote the time to making babies- and planning to spend a crap load of money on the venture that may or may not come to fruition. Its a waste IME.