You are looking at a slip that was printed by William Caxton (England’s first printer) on c. 1477, which is smaller than that of a toothbrush.
Mr. William Caxton in this sheet of paper praises a book that he just produced.
The sheet describes the book and then states that “you can get a copy at the Red Pale" (the name of his shop) in Westminster, London. You will not be disappointed because the book is “good and cheap", it further states.
Though not a mainstream type of advertisements that we see these days it is in fact stating words like 'good and cheap' which is a way to persuade people to buy that particular book which qualifies it as an advertisement.
Source: http://erikkwakkel.tumblr.com/post/55212549915/oldest-printed-advertisement-in-english-as-a-book
