Remove the lid from the top of the tank. Look closely just above the water line for the toilet’s manufacture date, or look on the lid. You may need to use a flashlight. The date may be an ink stamp, or imprint or etching in the wall. If the date is 1993 or earlier, this toilet will qualify for a $100 rebate. If there is no clear date stamp, take a photo of the numbers and letters that are stamped inside the tank and lid, and take a photo of the entire toilet. Toilets manufactured in 1994 or later usually have an ink stamp stating “1.6 gpf” on the toilet bowl, and they are eligible for the $40 rebate.