All I know, that they were popular during "M-A BEST" period, and Ayu always weared that, it was fashinoble. Some kind of trade mark "bought" Ayu to advertise their products, so, she weared them a lot. You were able to buy them in "DOME 2001" with all this staff like posters and others. And near them there was "A" simbol on a chain.
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