I don’t usually carry a pencil in my Graf von Faber-Castell leather writing case—a ballpoint or a fountain pen normally sits there. But I recently placed my GvF-C pencil and extender in the pen loop. The extender is silver-plated, and I polish it frequently. But ten days later, I took out the pencil and discovered this:
You can see the squared texture of the leather on the extender, from what I’m guessing was some sort of chemical reaction.
Though it may appear in the photographs that the metal surface is flaking off that’s not the case. A polishing cloth didn’t help much so it may require more aggressive treatment; I need to do some research first.