The Vintage Wrist Watch Company has dated this piece to the 1920s.
The T-bar is hallmarked for 1923. Each of the links has the lion has silver mark. The clasps appear to be period replacements.

There is also a silver fob with rose gold wash detail. The fob is hallmarked for Birmingham 1934. The fob measures 25mm wide, 25mm high.
The sovereign holder is hallmarked for Birmingham 1907, with a maker’s mark of JG for the Birmingham silversmith Joseph Gloster.
Total weight 62g.
The Vintage Wrist Watch Company has dated this piece to the 1920s.
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