Antique button question:

I’m hoping to use some buttons from Western Germany that are priced 10 cents for three.  I have no idea how old they are.  1930’s?  The card says Imported Mirror.  The buttons are clear and a bit sparkling. 

When I took the button off the card, I noticed that the backs of some of the buttons  are gold colored and some of the buttons have a residue and are a rather greenish color on the edges and brownish in the middle. 

Should I scrape off the brown and green?  I tried scraping off one before I thought about it and the result is a clear button?  Did I scrape off the mirror?  It may not glisten as much but there isn’t a huge difference.   Any suggestions or advice?

Can I launder these buttons?

Thanks so much.  Of course, I hope to wear the jacket in a couple of hours!  Another deadline, another miracle!