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The kanji on the box may even be done by the maker's wife.
I know a fellow who's Japanese wife is a master in calligrapyhy.

Nope all seperate masters in their own right.

I 'll put on my black hat here & say, not necessarily. The best J/swordsmiths still send the sword out to the polisher for sharpening & then the next maker for scabbard etc but not casting...