15ct "snuff" Pin

My mom gave this to me, not much info on how it ended up in her jewellery box. 15ct, pretty front design with rose/mine cut diamond in the centre, behind is a little compartment with a place to put a small photo of a loved one on cap of compartment. Simple clasp, just like an open jump hoop.
Hallmarked in Chester, it is marked first with the city's shield, followed by a 15, then a .625, then a fancy capital 'E' that resembles the date mark associated for 1905 and 1730. Although it resembles the 1730 date mark more, the style seems more like it was dated for 1905. The makers mark on it is F.B. I have not been able to track that mark down yet. Once I get a better camera, I will update a closer picture of the makers mark.