[Jim McDougall]

Hello Peter,
This is a most interesting anomaly!
I never dreamed that the Japanese would use a European blade in their swords in the manner that they found use in so many ethnographic contexts.
This blade, although notably reprofiled, is a British one from the M1796 light cavalry saber.
These were the first 'official' pattern sword introduced to the British army, and became famed for their resounding use in the Napoleonic wars.
They were somewhat replaced by the M1821 light cavalry saber, but with issues in that pattern, remained in use somewhat in certain contexts, particularly colonial as in India.

In India these remained much favored by native warriors, in fact so much so that these essentially 'obsolete' swords were absorbed by the Sikh's in the campaigns against the British in 1840s. The British were astounded by the deadly swordsmanship of the Sikhs, and more so when they discovered that their tulwar sabers held 'old' British blades.....the 1796!

I would imagine this blade might have found its way into the Japanese sphere a number of ways, however it is worthy of note that the Japanese swords were known in India in degree in trade situations through SE Asia in the mid to latter 19th century. Clearly these were not used in notable degree by warriors in Indian forces so possibly these may have been found in diplomatic or private enterprise circumstances.

It is amazing that the scabbard is modified in accord with the somewhat dramatic stock removal from the blade, which as seen in the British original, has a widened point known as a 'hatchet point'.