Ten-Yen:  historical notes

A couple of puzzlers with long memories brought Ten-Yen to our attention. Research revealed that it had been published in 1950 by Multiple Products Corporation in New York. Editions had also been published in England and Japan.

We were delighted to see that the ten pieces of Ten-Yen are actually a subset of our own popular design, Poly-5. Ten-Yen's unique choice of shapes and the colors assigned to each piece makes it a whole new adventure. So we've even kept the colors of our laser-cut acrylic edition faithful to the original. And when we went to investigate it beyond the original task of matching and non-matching of colors, we discovered a treasure trove of possibilities the original version never dreamed of.

The newly developed material fills up a 24-page activities booklet and leaves plenty of doors open for further research. Half a century ago they could not have known, for example, that Ten-Yen has 17995 solutions just for fitting the ten pieces into their tray. It took computers, and a clever program, and a clever programmer, to count all the possibilities.

A particularly challenging theme, suggested by Michael Keller, is to make the same shape with all 3 colors. We identified only 17 such shapes and offered a prize for any new ones or proof that no more exist. In January 2013, Andrejs Cibulis and his doctoral student, Juris Cernenoks, at the University of Latvia proved that 17 is indeed the complete set and won the award.

Other discoveries we added later were a pretty alphabet in 2009 by Ken Blackledge and the enclosure challenge. Solving the latter in 2014 won Robert Vermillion a prize. Robert also verified, in 2014, that our three shapes of 9 squares each that could be made in 4 copies each were, indeed, all the possibilities, out of 1285 potential figures.

Christmas 2002 was the world premiere of Ten-Yen's rebirth. We salute the original designers for their excellent and inspired work and are very pleased to have brought it back for new generations to enjoy.

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