There is nothing about Koiboii's fish that looks Showa. Definitely Sanke.
Long ago somebody began trying to explain the difference between Sanke and Showa to newbies by saying that Showa have black on the head and Sanke do not. ....Far too simplistic, but it sticks in the brain. It makes it seem so easy to differentiate. But, it's BS. It is desirable for Showa to have sumi on the head, and it is undesirable for Sanke to have sumi on the head. But these judging standards have nothing to do with the character or origin of these varieties. Sanke from 60+ years ago had sumi on the head... speckly, awful sumi terribly detracting from the fish. Bekko likewise got sumi on the head. As Bekko developed into a decent variety rather than a specklegoi, clean heads became admired. The goal is for Sanke to be the perfect Kohaku with a perfect Bekko overlaid sumi pattern. However, the presence or absence of sumi on the head has nothing to do with the variety. Through culling over many generations, it has become rare to see sumi on the head of Sanke. But, as we gain a deeper appreciation for the refinement of pigment and body structure, pattern becomes less important. We should recognize that sumi on the head of a Sanke (or a Bekko) is an aspect of pattern, not a defining varietal characteristic. .....On occasion, I think sumi on the head of Sanke or Bekko is actually an enhancement, but our judges are not at that point.... yet.