When you buy USP grade you are assured of 3 things:
1. The product was made to the exact specifications listed in it’s USP monograph
2. The manufacturer is FDA registered and licensed and the product HAS been approved(including the labeling/marketing material) by the FDA as meeting USP specifications.
3. The product was made in a FDA certified facility using cGMP(current good manufacturing practices) which are stringent to ensure lot to lot consistency.