This looks like a case where dating from photos will be a challenge. I am getting a feel that this is a marriage. The back chain looks much like an early 20th century watch or fob chain and does not seem "right" for the delicate front details. Something about it looks like this was put together from other parts, and re-purposed (recently?) into a lovely necklace, perhaps to make it longer or change the style.
Can you show the join of the two types of chain?
I am not sure, this is just what I get from looking at the photos. We have some jewelry dealers here who will give an opinion I am sure.