Here's the package. It reads simply, Black Eggs.
However, after peeling it there was no real difference in color or taste.
But that doesn't mean there isn't a difference. My mother-in-law handed me that bag and told me the saying about onsen tamago, a legend if you will.
If you eat one egg, your life will be extended by seven years.
If you eat two eggs, your life will be extended by fourteen years.
And if you eat three or more eggs, you'll be good until you die.
J and I agreed, we're stopping at two.