Steve Sly Japanese Works of Art has dated this piece to the 1880s.

Literature:
Typically, swords dedicated to temples and for presentations were made on special order for wealthy patrons. With extremely high quality mounts and fittings many older swords like these Ken style blades were used, and signatures added to the tangs.

The signatures were not intended to deceive, but were most likely a tribute to the quality of the blade and mounts.
The gold inlaid signature on this large Ken sword is Masamune, arguably Japan's best and most famous swordsmith.

The mounts although unsigned can possibly be attributed to an artist working in the mid 19th century by the name of Ishiguro Masatsune III.
For an almost identical example signed by this artist see :Dr Nasser. D. Khalili , Treasures of Imperial Japan , Metalwork II Plate - 161.

Condition report :
Superb condition throughout
Approximate Sizes :
Length Overall : 25" 63.5 cm
Length of blade : 14 1/8" 36 cm (inc habaki)
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Steve Sly Japanese Works of Art has dated this piece to the 1880s.
Specialists in japanese works of art from the meiji period 1868-1912
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