The piece looks dirty. You want to clean it to see it better.
Clean it so you can see what you have.
"Can I gather the evidence I need without cleaning?"
Photograph the piece as-is. Use angled natural light to read marks through dirt. A dry soft cloth only. Identify materials before any deeper cleaning.
Generally no. Document first. Try angled light to read marks. A dry soft cloth for loose dirt only. Wait until you know the materials before anything beyond that.
Yes. Aggressive polishing removes microscopic layers of metal. A faint hallmark can become illegible or disappear entirely. This is permanent.
A dry, soft, lint-free cloth. Nothing else. No water, no soap, no brushes, no polish until you know the materials.
