Antique British marine sextant by O.T. Olsen, Grimsby, late 19th century. • Full‑size professional navigational instrument • Ebony frame • Arc graduated to 105 degrees • Engraved scale with vernier • Original fitted wooden case included Condition • Structurally complete • Ebony frame intact • Metal components show normal age‑related wear and patina • Original index mirror and horizon glass present • Mirrored section shows visible age‑related surface wear (shown in photos) • Original shade glasses present Telescope • Telescope present; light visible through the optics • Not tested for navigational accuracy Sold as an antique scientific instrument, exactly as shown in the photographs. Shipping is primarily intended within the European Union due to size and insurance considerations. Keywords: Marine navigation, sextant, nautical instrument, scientific instrument, maritime, antique navigation, British sextant, ebony sextant