I don't think I have seen this exact link before. Double belcher links, interspersed with fancy links, which look like bows or starflowers. 
This antique guard chain has lots of lovely details, stamped with the same makers mark on the chain  and the original dog clip, which is attached with facetted jump rings. 
Wear it doubled, tripled, or even wrapped 4 times at the neck, the fact that this one opens out gives you all the options. 
Circa 1900 
Tested as 9ct gold (yellow in hue) 
Makers mark JB 
Weight approx 34.53g 
Width approx 3.4mm
Length approx 62 inches 
Excellent antique condition