The Elzevirs, as before stated, were pirates, who thought nothing of reproducing the full title-page, with the original publisher's name, and, when this is the case, it is often a matter of very great difficulty to distinguish between the original and the reprint. Again, when these printers did not wish to put their name to any particular work, for fear of embroiling themselves with the Government, they either marked it with the Sphere or else adopted a pseudonym. Thus Jean and Daniel frequently marked their title-pages "A Leyde, chez Jean Sambix," the Amsterdam printers occasionally adopted "Jacques le Jeune," while "Nic Schouter" was a favourite fictitious name. These pseudonyms are, however, much less numerous than was at one time supposed. The first reproduction of the _Provincial Letters_, by Louis and Daniel Elzevir, of Amsterdam, bears on the title-page, "A Cologne, ches Pierre de la Vallee, 1657"; that of 1659, by Jean Elzevir, of Leyden, has "A Cologne, chez Nicolas Schoute". A _Recueil de Diverses Pieces servant a l'Histoire de Henry III._, &c., bears "A Cologne, chez Pierre du Marteau"; _Les Imaginaires_, of the Sieur de Damvilliers, in its two parts purports to be issued "A Liege, chez Adolphe Beyers". _Il Divortio Celeste_, with other works of Pallavicini, dates from Villafranca, while other undoubted productions of the Elzevir press were ostensibly published "A Mons, chez Gaspard Migeot; Londini, typis Du Guardianis; Stampati in Cosmopoli," and so on, through a list which, difficult enough to remember, is yet not very extensive. It will be readily seen that the knowledge requisite for a collector to possess, if indeed he wishes to become a master of his subject, is of no mean order, for not only must he have the family pedigree at his fingers' ends, and be capable of detecting a pseudonymous or pirated work, but he must also be in a position to appreciate the "right dates," and to detect an improper head or tail piece when he sees it. Some books which pass as Elzevirs are in reality spurious, even though marked with the "Sphere" or other device; others, though coming from the press, are inferior editions, "not of the right date," as the specialist puts it.