This is a Green River Insect. This is a Fly trapped in the layers of rock well known from a classic site in Colorado. The preservation and detail is good.
It is Eocene in age, 50 Million years old from the Green River Formation in Colorado.
This formation is known for the insect fossils and leaves coming from that area. The fossilization is exceptional for these small invertebrates.
This one comes complete in this Glass Topped leatherette collectors case 4 x 5 inches.
The photograph in the frame is an enlargement of the actual insect inside the case.
This is the specimen you will receive.
Green River Formation