I have a zinc-beryllium iaito that I had made in Tokyo about 10 years ago that gets swung for 5-6 hours each week in MJER & Shinto-Ryu. On the left side of the mune (while holding the katana), there are hundreds of tiny dents going the entire length of the blade. There are no dents at all on the right side of the mune. I'm right-handed, my saya is made of the usual ho wood, & there is nothing but wood at the koiguchi. I don't really notice the dents when doing noto, but am starting to wonder if they might cause eventual blade failure.
I've been a professional engineer for 40+ years, & have worked with metals for most of that time, but I'm absolutely stumped. One other student in our dojo has a few dents on his mune, but nothing like mine.
Any ideas???