My electronic's instructor was talikng switches in class and I brought up about having to clean a switches contacts with a business card, he mentioned to use emery paper instead.
Yes I told him that gold plated "tungston"(spell check) would come off if something more abbrasive was used, the gold would come off and the life of the switch would be less. He dont know about pinball much. He was talking about Reeds for leaf switches and I never heard of Reeds, except for 2-stroke engines have Reeds.