On Thursday, June 20, 2019 at 4:14:18 AM UTC-4, GS wrote:

Whatever it was, I removed old NOS stuff like silver plated switches.
Around the switch was a piece of paper looking sheet. One side said towards
part. Any part sticking out of paper had turned black. I still have some
pads to stick inside sensitive equipment said to protect. Never tried them.

"Silver Paper" has been around since the 1800s, invented/developed in England when burning high-sulphur coal was common both for heat and for "town gas" that powered street lights. In that environment the "Plate" would tarnish almost overnight, requiring dedicated servants for its maintenance.

Still around today:

https://www.amazon.com/3M-Anti-Tarni.../dp/B00O89A21Q

As a related 'aside', fine silver is much more resistant to tarnish than Sterling or Plate-silver. So drinking vessels and those made to serve food typically had a fine-silver wash on the contact surface.

Peter Wieck
Melrose Park, PA