The grading systems for maple syrup are not standardized and the ones set by the U.S.D.A. (United States Dept. of Agriculture) are not manditory for the maple tree farmers. AFAIK, many countries don't have a grading system, or the grading system is different than here in the US. So look to the color and the darker the better.
Organic maple syrup should be certified and that should appear on the label. In a pinch any maple syrup will do, as long as it's pure (not maple flavored syrup). The darker syrup contains a bit more minerals because the sap (which rises in the spring) stayed in the tree until later in the harvesting season, picking up more nutrients.