When y'all meet your maker, tell him to build you some guts next time.
— The Engineer
The Operation Mecha Engine Badge is a cosmetic item for all classes. It is earned by completing your first mission of the "Operation Mecha Engine" Tour of Duty in Mann Up mode. It tracks a player's progress through the various Mann vs. Machine missions. The badge's level increases based on the number of Tours completed.
December 20, 2012 Patch (Mecha Update)
- [Undocumented] Added Operation Mecha Engine Badge