There is an antique Enigma Star quilt block at the Spencer Art Museum that is similar to Nancy's Enigma block. It is set straight instead of at an angle. I think Nancy's is more interesting.
I have not been able to find any other examples of quilts or blocks that look like Nancy's design. Maybe it is known by another name or was not popular.
I decided to paper piece my 6" block. I took pictures of the steps as I sewed the block but neglected to put the card in my camera so no pictures! My old camera warned me before letting me take pictures. Anyway, the block goes together in three diagonal rows which I hope you can see well enough in the photo. My pattern for the Enigma block can be downloaded here.