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You definitely want silver solder instead of lead solder and definitely nothing with rosin flux in it. Ideally you want silver bearing solder.
For pin holes you can usually just use a soldering iron...

Chlorinated water and harsh soaps can do that to silver and pewter.
Clean it with a toothbrush, and solder the holes with silver plumbing solder (non acid rosin core). Then file the solder back...