Prunes means and includes all sun-dried or artificially dehydrated plums, of any type or variety, produced from plums grown in the area, except: (a) Sulfur-bleached prunes which are produced from yellow varieties of plums and are commonly known as silver prunes; and (b) plums which have not been dried or dehydrated to a point where they are capable of being stored prior to packaging, without material deterioration or spoilage unless refrigeration or other artificial means of preservation are used, and so long as they are treated by a process which is in conformity with, or generally similar to, the processes for treatment of plums of that type which have been developed or recommended by the Food Technology Division, College of Agriculture, University of California, for the specialty pack known as “high moisture content prunes,” but this exception shall not apply if and when such plums are dried to the point where they are capable of being stored without material deterioration or spoilage, refrigeration or other artificial means of preservation.