ok, I feel like something of a nincompoop asking this, but here goes.
I really like the vinegar sauce served with the soup dumplings at Taiwan Cafe. I don't know what kind of vinegar it is and, while I can aften suss out ingredients in soups and sauces, subtle vinegar differences sometimes elude me. I know it's not cider, white or balsamic and beyond that my knowledge runs dry.
I bought something called "black vinegar" hoping to find a match and instead discovered something rather like worcestershire sauce!