Marilyn it's possible that "R" indicates Rolled-Gold. There are in fact lots of different marks on rolled gold articles, some a really confusing.
With Rolled-Gold articles, the thickness of rolled gold can vary, so its usually measured in Microns if the layer of gold is uniform, otherwise in Milliemes. It can be so well done that it's virtually indistinguishable from solid gold. There is a test you can do yourself with an acid testing kit to determine if the metal is Gold or Rolled-Gold.
