Lifter said:
USDA "probably" only grades what is in fact "edible", as the USA is a market driven economy, that, if its "edible" by grading, there's a ton of smoke and mirrors about the "quality" thing...
I gotta add my 2¢. All beef sold in the US has to be "Inspected" for wholesomeness (read: edibility). You can check the labeling on any package of beef, and somewhere, either on the plastic, on the box, on the paper label, and on the meat of sides or sub-primal cuts, there will be a circular stamp that reads "U.S. Inspected" with some other stuff. This is required by law.
"Grading" (read: quality) is optional. Most meat packers will have their meat graded. From what I remember in college, USDA Inspectors look at many features, including the animal when it's alive, after it's slaughtered, the quality of marbling, etc. There are only six grades: USDA Prime, Choice, Select, Cutter, Canner, and Institutional. The last three you will not find in stores, as they get sent to canneries (Dinty More Beef Stew, Canned beef broth, dog food, etc.), or some place that doesn't have to worry about what their "customers" have to say about the quality of meat. USDA Prime is the best of the six, with Choice second, and Select third. USDA Prime is hard to find in a grocery store (I've never seen it), but I wouldn't be surprised if a friendly butcher would order some for you. USDA Choice and Select are what normally shows up in stores. Certified Angus Beef, from what I was taught, is somewhere between Prime and Choice, but isn't really a "grade".