Hi Gene,
You're most welcome and the pleasure is mine too
Ok, I've just received the response of my Japanese friend, and this is direct from Tokyo and this would supplement what Stekemest and Drdavid have mentioned --
He says that the name of the manufacturer is inscribed at the backside of the mirror. I'll ask him later to elaborate on this.
He also "guesses" that the mirror was made around 110 to 200 years ago. Don't know whether "110" was a typo and whether he meant "100".
As for the 10 characters, his preliminary reading is: [a] 1st to 3rd Kanji is "TENKA ICHI"; [b] 6th to 7th Kanji is "INBA"; and [c] 9th to 10th Kanji is "SHIGE YOSHI".
Again I'll ask him later what would be the English translation and/or transliteration of the above.
More later ...