Three diamond-set ring mounts

Three diamond-set ring mounts, missing centre stones, one rectangular form with a ballerina-style mount set with tapered baguette-shaped diamonds in white gold, size M, another mount for a rectangular-shaped stone set with three graduated baguette-shaped diamonds to each shoulder in platinum, size O, another for a pear-shaped stone with a tapered baguette-shaped diamond to each shoulder in platinum, size M