I can't say for sure exactly what year the switch from R12 took place, I guess I didn't think it was important. This system has had 134 for several years, and since the two refrigerants do have slightly different characteristics, I thought some of the experts might feel the total capacity might be just a bit different for 134. Maybe not. As for a data plate, I haven't looked for one because I wasn't aware that Deere might supply the refrigerant capacity on a plate somewhere. I guess if I were as knowledgeable on Deere as some, then I wouldn't need to ask questions.