people have gave it the name "diving board" because of its appearance. Like tat said, its simple a us to jap converter. Yours is a revision that works with the duo. The diving boards without that yellow wire do not work on the duo. It usually sells for $100 and up on ebay.
WOW,, 100USD
it's just a single sided FR4 material pcb with some fixtures on it.. it's work like USD0.25 as for what it's worth, hahaa,,,, anyway,, I think there's a converter that's in white / purple that I've seen many years ago, haha looks better,,