The image above is of a holochroal eye of an Asaphus expansis trilobite fossil. It was found at Gillberga Quarry on the Baltic Sea island of Öland, Sweden on May 5, 1986. The fossil dates to the Lower Ordovician Period. I believe it was found at the Volkov Stage (Gillberga Limestone or old name Hjorthamn Limestone).
The original fossil was found by Dr. James Conkin and later prepped and photographed by Kenny Popp.
Learn more about this locality:
http://sarv.gi.ee/igcp503/IGCP503/page/Oeland.pdf