The mei on the left tang, as far as I can figure out so far, are the Koa Isshun Mantetsu for the first two characters. The third character is the kanji for 10. The fourth and fifth are still hiding from me in all the lists of kanji I've been pouring through. The sixth is, I believe, a poorly chiselled number 6 followed by the last character which is the kanji for month.
So, I'm guessing it was made in June. The spring was thought to be the most auspicious time to make a blade. I wonder if they just marked them ALL April, May or June?
The red paint looks almost like fingernail polish. I doubt if the guy who brought this sword back ever even saw the tang since I had to work pretty hard getting the sword apart. I thought the paint was probably something the manufacturer put there.
Steve