In 1994 Canada issued a booklet of Greetings Stamps, billed as the world's first customizable stamps. The self-adhesive stamps were issued in booklet format only, ten stamps, five with Canada on the left and five with Canada on the right. The circular center was blank, as the circular labels provided were to be peeled and stuck on the stamps, to suit whatever the mailer wanted. Seven different labels were provided, with a total of 35.
Complete inside of the booklet:

Front cover:

Inside cover:

Back Cover:

More to come... the challenge of collecting used combinations!