I know what it is in general terms of course. But I mean specifically what does the M7 mean. I certainly can't just go to digikey and order an M7 diode because such a part does not exist. I'm making a rugged arduino clone (using kicad) for my own use and intend to put a fuse or possibly resettable fuse in front of that diode so as it doesn't burn out etc... so I have thought of that.
It appears to indicate that the diode must have a 1000v reverse voltage.
See here for the circuit (see the external power supply circuit): http://arduino.cc/en/uploads/Main/arduino-leonardo-schematic_3b.pdf