Ummm, is this a trick question???
Sounds like a third center brake light that has been standard on cars since the mid 80's and all vehicles since the early 90's.
Factory wiring to that light would be separate from the rear turn/brake lights since you don't want it flashing with the turn signal . Some aftermarket center brake lights used a logic circuit (as WilleyB mentions) since the aftermarket add-on units normally did connect to the existing turn/brake wiring.
No muffler bearings involved.