Well, if it is silver plate, it sounds like it disolved through the silver plating and then disolved some of the base metal, or metals. Hence the dark color. Why not try what Lou suggested in another thread, he said this:
" Perhaps make a streak on some porcelain? If you add a drop of 20% nitric acid and the metal dissolves and gives a clear solution, it's likely silver. Add a few drops of 20% HCl and if any precipitate forms, then it's most likely silver. Add many drops of conc. ammonia and if the white precipitate dissolves, it is definitely silver.
Any green or blue and it's a base metal."
Randy
