Nippon marking and backstamp

by Peter carr
(Boston MA USA)

Hi,

I have no idea what era or who made this.
Very faded markings on the back.
It has the letter "M" under "NIPPON" with no wreath and just the 2 markings on either side of the M(see picture).
I tried my hardest looking up what that backstamp/mark is with no luck.
Please help?