Is it the Nathos Auto?
There’s no such thing as Nathos M.
There’s Nathos S+, Nathos Auto and Nathos Nova.
EDIT - Or have you got the first generation Nathos M that came out in 2008. Forgot about that one.
EDIT 2 - Here’s info for the Nathos M and what it is privately.
“The Nathos M is equivalent to a Phonak Versata with addition of echoblock but constructed in a Naida SP casing.”