The specimen below is of a Nautiloid called Pleuronococeras sp. and comes from the Ahbach formation (Devonian, Givetian stage) near Üxheim, Germany. Pleuronococeras is an open coiled species of Cephalopod that looked like a bracelet if one were to excavate a good specimen. This fossil is mostly crushed but still is a good example of the species. You can see that the crushed segments had some decoration on them in the form of linear growths parallel to the shell direction.
Thanks to Nils for the fossil. I don't have too many non-straight nautiloids from the Devonian in my collection.