This is an unsigned Japanese katana with a blade length of 62.6 cm and a curvature of 1.3 cm, showing a well-balanced and practical sugata.
The blade features a predominantly suguha (straight) hamon with subtle undulations, presenting a calm and refined appearance. The jihada appears to be a fine and tightly forged ko-itame, indicating careful traditional craftsmanship.
The nakago shows three mekugi-ana, a common practice for older swords adapted for later use. The patina of the tang is consistent with considerable age.
Based on the overall shape, forging characteristics, and tempering style, this blade can be reasonably attributed to the Muromachi period (15th–16th century), likely within the stylistic influence of the Yamashiro or Yamato traditions, known for their refined suguha hamon and elegant workmanship.
The sword is mounted in Imperial Japanese Navy officer’s mounts, indicating that this traditionally forged blade was later selected and remounted for naval service. Such reuse of older, traditionally made swords was common among officers who preferred classical blades over contemporary mass-produced examples.