Back in the 1970s / 1980s, Walkers Crisps packets used to have facts from the Guinness Book of Records on the back, giving you something to read while you ate, though repetition was obviously a problem. The packets at that time were transparent in places, so you could see the crisps you were buying (i.e. keep an eye out for packets with abnormally huge crisps inside, or unpleasant-looking green crisps). Nowadays, the contents are hidden from view, so crisp-buying is always a gamble. The records have been replaced by various special offers - Free Books for Schools is a recurring example.