Never clean silver oxide from your silver connectors! Silver oxide is just as conductive as pure, polished silver.
Western Electric used to silver plate many of their tube pins. One of the reasons, besides super conductivity, is that they wanted very low maintenance on their leased equipment, especially in somewhat harsh environments. Silver oxide, unlike rust, pitting & corrosion from other metals, is a very conductive &a desirable by-product of the silver oxidation process. It would be "sacrilegious" to clean the tube pins on old Western Electric tubes!
My $0.02,
Pete