The Vintage Wrist Watch Company has dated this piece to the 1930s.
The chain measures 28cm long including the T-bar and the clasp.
The T-bar is a fairly modern replacement.

The chain also has a shorter chain attached, with lion silver marks, and a silver and enamel fob, GWR 25 Years First Aid Efficiency awarded in 1947 to Frank Everett. The front of the medal has a pale gold wash.
Total weight of the chain and the fob is 35.2g.
The Vintage Wrist Watch Company has dated this piece to the 1930s.
Specialists in antique and vintage wrist watches and pocket watches
You can view the stock and full dealer information on the The Vintage Wrist Watch Company Profile Page