Your latest shipment of chicken has some items with usda stickers and some items with usda grade stamps. what is the difference in these items?

USDA actually has several stickers/labels/stamps that could have different meanings. However, the sticker most likely indicates that the chicken has passed for inspection while the grading stamp means that the poultry processor also requested to have the quality of the chicken evaluated and graded.

The USDA has separate programs for the inspection and for the grading of meet. The former is mandatory and guarantees the wholesomeness of the meat. This means that the animal from which the meat was taken from is not diseased and that the meat is clean and fit for human consumption. Inspection programs are paid for by public funds. 

However, USDA also has a grading program, which is paid for by the meat processors. The grading program checks and classifies the meat according to its quality (e.g. flavor, juiciness, and tenderness). Poultry with a Grade A poultry for example is one which does not have "defects" such as feathers, discoloration and bruising.