In the past, maple syrup was graded based on its color and flavor. Grade A syrup was the lightest in color and had the most delicate flavor, while Grade B syrup was darker in color and had a more robust flavor. Grade C syrup was the darkest and strongest-flavored of all.
However, in the 1950s, the USDA decided to simplify the grading system for maple syrup and eliminated Grade C syrup. At the same time, they also raised the standards for Grade A syrup, so that only the lightest-colored and most delicately flavored syrup could be labeled as Grade A.
As a result of these changes, Grade B maple syrup became a thing of the past. However, there are still some producers who make syrup that would have been classified as Grade B in the past. This syrup is often sold as "dark amber" or "robust" maple syrup.
So, if you're looking for a maple syrup with a more intense flavor, you may want to look for dark amber or robust maple syrup. These syrups are similar to Grade B syrup, but they can vary in color and flavor from batch to batch.