Nice find!! I'd guess that your ring was handmade either from a stainless or Monel hex nut. This was a popular pastime when I was in the Navy. Monel is a stainless steel alloy and will most likely not be very attracted to a magnet due to a very low iron content. These rings were usually very heavy mainly because one tired of filing and sanding after acquiring a ring like shape. Another ring variation was to hammer a silver quarter continually with a table spoon. This in time will roll the outside edges and makes a ring similar to a mans wedding band. It takes a while but with careful drilling and filing to remove the center a neat ring can be created. Two Dogs