[ale42]

On which OS? On Windows, with the Swiss German layout AltGr+m does nothing. Probably the same on US ones.

[Tuna-Fish]

All of them. And it's not just an os thing, it's usually printed in the bottom right corner of the M key, the same way € is in the corner of the E key.

[voidUpdate]

Depends on your layout. My € is in the corner of my 4 key, and the only alt letters I get are accented vowels, ¦ and €. I use a UK English keyboard and windows