C.1890-1900. An exquisite lapis lazuli and diamond gold locket. Simple in design, yet what makes this piece opulent and refined is that the locket is double sided. Deep royal blue colored lapis lazuli is surrounded by a row of old cut diamonds on each side, and the chunky and bright old mine cut diamonds at both's center deserve the attention. The original diamond bale also matches the double sided motif. The bale is adorned with six small diamonds on each side. The total weight of the diamonds is approximately 4 carats. 
One side of the lapis appears to have a bit more organic pattern with a slightly lighter color than the other side. (see the photo) The locket is crafted in 18k subtle rosy gold, and the stones are set in sterling silver. The locket opens on one side, and it now contains a sepia portrait photograph of a beautiful lady that is easily removable if desired. It closes with a good snap sound. The locket bears French owl hallmarks with the number '75'. They are seen on the side when the locket is opened. This French hallmark indicates that the locket was brought to France, and was examined by the French assay office around/since 1893. The French owl hallmark represents a gold piece that is imported from a country whose standards do not follow the French one. And '75' is a region number for Paris, so it shows that the locket was marked in Paris. 
This medium sized locket will look gorgeous with your silver or gold chain. Overall it is in great condition, and ready to be worn. 

Total Drop (N-S) : Approximately 40mm (1.57") including the bale 
Width : Approximately 23mm (0.90")