Ron,
in some cases, when corrosion has eaten away too much material, signatures remain guesswork. In this case, I also thought the first KANJI might be TAIRA, but I have no books on blades or signatures to check that.
What you could try would be making photos on a plain dark background, in a dark room and spotlights (not too strong to avoid glare) shining from the side.
I found that extreme magnification often does not help much.