Morning Ray. Like you I find these things interesting and it is a 'loose end' in an otherwise tidy package of history!
I appreciate your explanations but in this case at least there is not much to get wrong?
Certainly I have the first photo album of the 1968 All Japan show
Certainly Peter knows what he is talking about
Certainly you did your research
But this Gent, Glenn Takeshita has this maruten sanke on the cover of his book 'KOI' and inside he has several pictures of the show itself and the fish again in the show vat. And he refers to the event as " the First All Japan held in late 1968". And he even has photos of that classic shot of the sky scraper trophy wall. ??
The caption on the picture of the maruten I posted reads " This Taisho Sanke was the Grand Champion of the first All Japan Koi Show held in Tokyo in 1968"
The body on the maruten 'looks' pretty good and the stuff of a major winner- especially back in 1968! And it looks to be of a decent size although the author never mentions size of this fish.
Yet 'your' sanke, and now Peter's sanke seems to have the weight of being shown in several sources as THE GC?
Very intriguing!

JR