Item description:

Remade to new standards.
Now mods all 8 slots and rehashs the file after.

In order to not look dodgy on your achievement list you may want to unlock the inferno achievement first as the weapon one will follow directly after since inferno gives you the genocide gun normally. Don't worry about modding slots you aren't using, it's harmless.
I recommend mission 2 for achievements as its short and relatively easy using the highest version rocket launcher, so you can get 1000g in about 10 mins replaying the mission once per difficulty.