I did a quick search on mindat for Silverton and there is reported silver, gold and galina in the area. Heck, why name something SILVERton, unless there is something that looked like silver in the area. I was hoping to see platinum on the list as well, but it did not jump out at me. Still, it would be interesting to find out what mineral(s) are in these nuggets (or melts). I would suggest finding a jeweler or pawn shop with an XRF to do a quick test. That will immediately solve the mystery. Good luck and my fingers for you.
Here is a nugget from ore metal detected at a historic silver mining camp called Cobalt, not far from a spot I know Jim has previously investigated. ;-)