This is a fossil nautilus of the species Syrionautilus libanoticus from the Cretaceous of the Lebanon.  As a special feature, this nautilus shows a partial preservation of the soft tissues. Klug et al., 2021 describe similar specimens that show also preservation of the soft body.
The publication is freely available, the link can be found below.
The Nautilus itself has a diameter of about 47 mm.

Klug C, Pohle A, Roth R, Hoffmann R, Wani R, Tajika A. Preservation of nautilid soft parts inside and outside the conch interpreted as central nervous system, eyes, and renal concrements from the Lebanese Cenomanian. Swiss J Palaeontol. 2021;140(1):15. doi: 10.1186/s13358-021-00229-9. Epub 2021 Jul 23. PMID: 34721283; PMCID: PMC8549922.

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