The 1/60th is a measure of the amount of gold in relationship to the total weight of the item. Just like your 1/20th piece. Any time you see R.G.P., that stands for "rolled gold plate". This means a thin layer of gold fused over base metal. The maker''s mark >M-H< is the manufacturer of the piece, in this case Mc Grath-Hamin of Providence, RI. I think they are still in business. I don''t think your two blue stones are real but they need to be tested to be sure.
Keep them coming, eventually I''ll be stumped but there a lot of knowledgeable people on this forum that are happy to help you.
"Gold there is, and rubies in abundance, but lips that speak knowledge are a rare jewel."