Czech costume jewelry - how to clean?

Hi everyone - I was wondering about the best / safest way to clean these? I have found similar which say these are rhinestones, and wanted to ask to make sure I don't ruin them.

The earrings are marked "Czecho slovakia" on the back knob. I can't find any markings on the ring, and am only guessing since it came with the earrings. They are obviously plated metal of some kind. It's a shame so many stones are missing from the ring, but hopefully someone will want it for repair.

Thanks - appreciate any info you can share. Hope the pics are okay. My phone's macro function is not the greatest.

 

They are nice!
I'd first scrape the green on back with a wooden toothpick, then rub all over a soft toothbrush sprayed with window cleaner (best with some amonia in it), but not too wet!.
Let dry thoroughly and polish with a sushine/silver cloth.

 

Do not get the rhinestones wet, moisture on the backs will cause the foil to turn black and destroy any value.

Use a very soft toothbrush, dip it in rubbing alcohol, shake off the excess and brush the front of the stones. Immediately blow dry with a hairdryer on the cool setting. This will clean the stones but not harm the foil backing.

 

Thank you both! That's exactly what I was worried about. I've seen old rhinestones with the back layer flaking off, and didn't want to risk it. I appreciate the info.