Need help cleaning heavily corroded brass buttons

[ColtsPop]

All, please let me know the best way to clean the attached flat button. Soap and water isn’t cutting it.

I was hoping to be able to read it….

 

[fyrffytr1]

That doesn't look like brass to me. More like pewter or tombac. I don't know of a good safe way to clean either. Hopefully someone else here will. In the meantime, until you know what it is actually made of don't do anymore cleaning.