This is a nice example of paleozoic cephalopod

 Fossil group: Cephalopoda

Belongs to: Endoceras
Other version of taxon: Proterovaginoceras incognitum
1821     Orthoceratites duplex — Wahlenberg, 1821
1968     Endoceras duplex — Balashov 
2012     Endoceras incognitum Schröder 1882 

Stratigraphic range: Middle Ordovician (within ca. 470.0 – 458.4 million years)(Darriwilian) deposits of Lasnamagi quarry near Tallinn, Estonia. No reconstruction. Shipping worldwide $20.