Professionally cleaned (I am a former professional museum conservator). Does have a microcrystalline wax coat applied to prevent further oxidation.
The button is stable and ready for display.
US quarter shown for scale.
I have terrible eyesight, so I can work with these materials only a few hours per day and under extreme magnification.
Mechanical cleaning methods are all I use (never chemicals). I do sometimes coat the artifacts in a neutral microcrystalline wax, but only if required and it will be noted in the description.
From a smoke-free home.
I am visually disabled. If I miss something, it is NOT intentional.