Hi.
The images of the locket and marks embedded.Btw.links to commercial sites are not allowed here.
The closest I can tell is year 1882 for Birmingham,but the first letter in maker's initials is difficult to decipher.
Not sure for Birmingham.Lacking town mark and duty mark is possibly because of small item, but I am not familiar with those exceptions.
Regards
![Image](https://abload.de/img/s-l160012pj9j.jpg)