It is granted for constructing one of each custom weapon. They include the:
- Oddly, none of the weapons in the picture (a missile launcher, a sawed-off shotgun, a pistol, and a BB gun) are custom weapons.
- Locations that provide most, if not all, of the components required for custom weapons include Lucky's, Horace Pinkertons lab in the Rivet City Bow (which require items to be stolen), Craterside Supply, Old Olney Underground.
- Selecting the level 26 perk, Warmonger, makes all custom weapons available to you without having to find their schematics.
- Sometimes after you have made each weapon, the game doesn't give you the achievement/trophy. However, this may be due to finding one of these weapons rather than actually constructing it. The bug can be resolved by taking all the components and making all the weapons in one time.