There should be a square sticker or metal plate that tells you the model # the #'s that comes close to the multiplecation of 12 =to tonnage,example ( asbv036g-1 the 36 = 3 tons 12x3=36 (gdhe420-1 = ==3-1/2 tons cooling 12x3 plus 6-1/2 ton = 3-1/2 tons the serial # tells the year it was made.....080808 , the first 4-#'s tells you the month--- for 4 #'s this is aug.- year 08 !