Draduated diamond collet necklace

The single row of 57 diamonds of square and rectangular cushion, old oval and pear cuts, each close cut-down collet set in silver and gold, upon an oblong cluster clasp with three stones to middle bordered by a line and flanked by twin stones to either side, also cut down collet set in silver and gold, very approximately 63cts in all
Length 39.5cm / 15½''
Weight: 44.5g