What bookdealers really mean. A dictionary by Tom Congalton and Dan Gregory (Between the Covers), with additions from other sources
Also called a ticket. In days of yore (that would be, before now) new bookstores would often have a small, usually discreet label that they would affix to one of the endpapers in the new books that they were selling. In some instances they are collectible, in some instances they are a nuisance, and in any case they indicate where a certain copy of a book originally sold at retail.
Etiquette de libraire
On trouve parfois dans certains livres une étiquette collée à l'intérieur des plats portant le nom et l'adresse du libraire qui les a, à moment donné, eu entre les mains.