This dagger is one from a group known to collectors simply as "Yamamoto daggers". During World War II, Admiral Yamamoto Isoroku (1884-1943), Commander-in-Chief of the Imperial Navy petitioned the Imperial Hosehold agency for a sum of money to be presented as a stipend to members of his fleet who had distinguished themselves in battle. However, due to financial hardship brought on by a costly war Yamamoto soon found that the resources were not available for his fund. Instead, he was able to commission swordsmiths to forge a group of twenty daggers on behalf of the Imperial Household to be presented in lieu of the stipends.
This dagger was presented to a high-ranking American diplomat following the war in appreciation for his service as an official liason between the American occupation forces and the Imperial family. This dagger is thought to be the earliest of the group of twenty and was in Yamamoto's possesion. Reputedly it was received directly from Yamamoto's widow.