In 2015, I grew two plants from TPS labeled as Blue Shetland.  Apparently, Blue Shetland potatoes are also known as Shetland Black (correct me if you know otherwise.)  Either way, the tubers that I harvested were really unexpected.  The first plant produced the tubers pictured below; a strange double lumped/ hourglass tuber shape.  I like the skin and flesh color, so I kept it to plant in 2016.  So far, this is one of the best keepers of all my 2015 TPS tubers.  The second plant did not produce anything worth harvesting.  There were only a few pea-sized tubers clustered next to the main stem.  I have some more Blue Shetland TPS and some TPS labeled Shetland Black.  It will be interesting to compare plants from these seeds in the future.