No maker's mark.  Incised with STERLING, as shown.  Please review the photos before bidding.  There are irregularities in the stone.  I do not know what the stone is or if the irregularities are natural or not.  It is sold as shown.  Ring is size 8, and the stone is about 5/8 X 7/8 inches.  The setting is about 1-1/8 X 3/4 inches.  Buy more and save - If you are buying multiple items from us, just let us know before you pay, and we will combine shipping to save you money.