Unfortunately the scan doesn't show precisely how it sits, but imagine the piece creating an X on the body front and back, with the top chains passing over the shoulders and the lower chains underneath the arms, connecting at the back with a catch. The jeweled central junction, here holding an amethyst and surrounding garnets, would sit at sternum level.
How cool is this? The only cognates I could find were Pancho Villa's crossed bandoliers (equally eye-catching for different reasons) and some cheapy-cheap diamante body harnesses, the sort of thing that the hired entertainer might wear at a certain kind of bachelor party.
The style deserves a more discerning audience. Women of all shapes could rock the links off a heavy gold version like the Byzantine one above, with a black or bronze jersey column dress or even a dead-simple white sleeveless t-shirt. The look? Totally Gallo-Roman chic.