Unfortunately I now need help translating the translation. The first three characters 主水正 seem to match "Masakiyo an Yasuyo who enjoyed subsequently a veritable program consisting of recommendations and orders, the honorary title Mondo no Shō (主水正) was granted to him on the 13th day of the seventh month of the same year (1721)," as stated on page 320 of Index of Japanese Swordsmiths A-M. I haven't found a reference for the fourth symbol, . Does the last symbol..?
Wait. "Stephen has it, good job. Mondo (no) sho Masakiyo. very famous smith. Hos swords are worth $10-50,000 and more
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Mark Jones
nixe@bright.net"
Question answered? It is an exquisite sword. I will post more images of it later.
Thank you.
Francis L.