Mann Co. Supply Crate Key (Team Fortress 2) Mann Co. Supply Crate Key is one of the items in the Team Fortress 2 game that is used to open Mann Co. supply crate. This item can also be resold on the Steam community market to top up your Steam wallet balance. More profitable than buying Steam Wallet vouchers Purchase Terms: 1. Must include an active Steam Trade Offer Link at the time of purchase to speed up the process. For questions, please use the Send Message feature