Hi Dan the first mark - "SGP" in a rounded edged triangle is -THE PANIS GALLERY (Stavre & Gladys Panis) (Arts & Crafts Silversmiths & Jewelers, Falmouth, MA, USA) - ca 1932 - Present.
I will have a look over the weekend and see what I can find on the other mark.
I would have love to see a photo of this piece and I am sure others would to :-(
