Two different batch dates of the original Terra formula. The only difference between the two dates is that they were pulled out of the furnace at different temperatures. This resulted in slightly different rod colors. The formulas and all other procedures were identical to each other. There are two small differences in the procedures of these test batches and original Terra. Original Terra was hand drawn out of the furnace where as these test batches are mechanically drawn. Original Terra had an older furnace charging procedure that we no longer use. We will leave it up to you to decide if these differences contribute a significant change or not.