Hi Steve in answer to your question about hallmarks. First up, the 9ct stamp is the purity mark, it means the brooch is 9 carat solid gold. You can find the millesimal value here.
The sponsor's mark is:
SYDENHAM BROS. Birmingham, UK - ca 1900 - 1920s
The safety chain, also gives you a clue to the date. Although the safety pin (at the end of the chain) was patented in the mid 1800's, it wasn't used in jewelry until the 1890's.
Thats why it's important when you invest in Antique Jewelry to make sure the findings such as safety chains are original to the piece.
