This is a high-voltage contact from inside a decades-old power supply. I find that ripping apart electronics being thrown away is fabulous as both catharsis after and procrastination from schoolwork, with the added benefit that I occasionally find something incredibly cool, possibly useful, or silver. In this case, its the latter--silver has the highest conductivity of any metal, plus good resistance to tarnish (except around sulfur and sulfur oxides). So while this contact is still quite shiny after decades of existence, the silver sulfide tarnish is visibly building up, albeit long after the useful lifetime of the device itself.