A diamond necklace, France, circa 1900, the articulated collar set with a series of graduated

A diamond necklace, France, circa 1900, the articulated collar set with a series of graduated circular-cut diamonds, the detachable central diamond weighing approximately 1.10 carats, spaced by bar links set with rose-cut diamonds, mounted in silver and gold, length 36cm, French assay mark for 18ct gold, French maker's mark B&M with star