This is a signed Japanese sword bearing the mei “Jumyō” (寿命), a name associated with a long-standing lineage of swordsmiths of the Mino tradition. The Jumyō group was active from the Muromachi period into the early Edo period, producing blades known for their practical construction and durability.
The blade measures 54.7 cm in length and features a straight hamon with a clearly visible itame-hada. The overall workmanship reflects the characteristic Mino style, emphasizing functional strength and refined simplicity rather than flamboyant midare tempering. 
The nakago retains a well-cut signature and shows orderly yasurime, consistent with early Edo period workmanship. Based on the shape, signature style, and overall construction, the blade is most reasonably attributed to the early Edo period (17th century), rather than an earlier Muromachi example.
The sword is mounted in Imperial Japanese Navy Kyu guntō koshirae, the Western-style mounting that was adopted during the Meiji period.
The combination of a traditionally forged Mino-school blade with naval military mounts illustrates the continued use and appreciation of classical swords in modern military service.