Antique Victorian 12kt gold gilt & 10kt solid base genuine citrine pendant

This piece is formerly a brooch and rear is still fitted with hand wrought C-catch and tube hinge but pin is missing. Can be worn as a pendant thanks to open loop. The rear base ring is constructed of guaranteed solid 10kt gold while everything else built onto it is 12kt gold gilt brass. Framed in the center is a gorgeous genuine pale yellow citrine gemstone. Piece is further enhanced with hand-etched detailing and three-dimensional frame and bow. There is a slightly obscured maker's mark which could be a combination of several possible letters. Impressive weight of 13.81 grams-it is difficult to estimate what percent of this is made up by the solid gold base. Please see photos for measurements in inches.