An Austrian Gasser revolver Model 1870/74. Very skillfully engraved with gold inlays and I believe ivory grip plates (and tools).
The insignia translated to English reads: “Revolver of the Crownprince; model Gasser-Kropatschek; presented as a custom-made gift from the Leopold Gasser Factory in Vienna.”
I don’t know much about Austrian royal history, but I think this pistol may have belonged to Rudolf, Crown Prince of Austria. He is notable because WWI may never have happened had he not ended his own life before becoming Emperor.