It seems he was supposed to start the game with this item, much like his trench coat and fedora.

Robotic bits, an eye-slot piece of clothing for Nick Valentine that gives +1 Perception.

Cait's bandolier (ID: 001921D8): Although this armor add-on will appear when equipped, it has no world model and should not be dropped.

While the goggles and the helmet are still in the game (as separate objects), the scarf was cut entirely, though it may have been replaced in concept by the different bandanas.

Light, medium and heavy variations of the metal helmet consisting of wraparound goggles, goggles plus helmet and goggles, helmet plus scarf combinations.

In the final build of the game Elder Maxson wears a unique coat, the mesh of which includes the BOS officer uniform.

Maxson's cape: Appears as an armor add-on fitting on the BOS uniform.

In the final build of the game Lancer Captain Kells wears a unique variant of the Brotherhood fatigues.

Kells' coat: Appears as an armor add-on fitting on the BOS uniform, based on a reskinned version of Piper's Red leather trench coat.

Most likely replaced by the Science scribe's armor in the final build of the game.

BOS lab coat: Appears as an armor add-on fitting on the BOS uniform.

Fallout 4 concept art mods