P425 is a designation found on many crates and containers belonging to Traxus Heavy Industries and/or the UNSC Defense Force. The designation may be interpreted as a serial number or a code denoting the crates' point of origin, their destination, the nature of their contents, or a particular type of crate.
Crates with "P425" printed on them are often found where Traxus or its products are involved, such as the many Traxus industrial sites or construction projects in the East African Protectorate on Earth. For example, several of the crates were scattered on a hilly dirt road near Voi Municipal Water Pump House 03 along the Tsavo Highway, in the motor pool of the UNSC military base Crow's Nest, and in the industrial warehouses of Voi.
- P425 appears to have been a generic stock decal used by the level artists in Halo 3, as it is found in many objects with little in-universe connection to each other, including 2 HEV pods landed on the Ark's desert region, next to the crashed Longsword fighter, in the level The Ark.
- P425 is a 7 reference (4+5-2=7).