The Plug-In Prospector is a community-created headwear item for the Engineer. It is a robotized version of the Ol' Geezer.
The Plug-In Prospector was contributed to the Steam Workshop under the name "The Ol' Greaser".
May 17, 2013 Patch (Robotic Boogaloo)
Steam Workshop thumbnail image for the Plug-In Prospector.