I've had this gorgeous Sterling necklace for quite sometime and have not been able to identify any if the marks aside from 925S. I believe it is in a Modernist style and was possibly made in either Norway or Denmark due to the 925S mark. There are two marks on the pendant of this piece:
1) One mark appears to be a large "G" with an "S" inside
2) The second mark on the opposite side of the pendant looks like J.T. 925S. I'm not sure it is a "J" because the lower section of the letter seems to curve upward.
I've included one photo of the necklace and each mark in the hopes someone can help me identify either mark. Thanks so much for taking a look! Annie