I wish y'all could see how bad I'm kickin' your tail.
— The Engineer on his ability to see in the dark
The Mining Light is a cosmetic item for the Engineer. It is a faintly glowing strap-on helmet lamp attached to his regular hard hat, similar to those used by miners.
May 21, 2009 Patch (Sniper vs. Spy Update)
- [Undocumented] The Mining Light was added to the game.
September 30, 2010 Patch (Mann-Conomy Update)
- The Mining Light was added to the Mann Co. Store.
- [Undocumented] Added a community-contributed description for the Mining Light.
- [Undocumented] The Mining Light can now be uncrated with Unusual quality.
January 25, 2013 [Item schema update]
- The Mining Light was removed from the item drop system and Mann Co. Store, and can no longer be uncrated with Unusual quality or crafted. Crates with the possibility to get the hat are unboxed in normal quality. 
September 10, 2014 Patch
- Updated the
equip_region for the Mining Light.
- [Undocumented] Updated the
item_type for the the Mining Light.
September 25, 2014 Patch
- [Undocumented] Added the Limited attribute to the Mining Light.
- Typical mining helmets have either a fitting attached to them or molded into their surface, for the purpose of holding such a light. Since the Engineer wears a construction worker's hard hat, the light must be attached by non-conductive leather or nylon straps.