Jean de Sperati (1884-1957) was a French forger who had to expose his own stamp forgeries. In 1942, when Sperati sent a package of supposedly valuable stamps to a stamp dealer in Lisbon, French customs seized it. They charged him with trying to avoid customs payments and took him to court. In court, French criminologist Edmond Locard testified that the stamps were at least worth 223,400 French francs. Wikipedia
Jean de Sperati (or Giovanni Desperati) is probably the most dangerous forger of stamps, some even call him the 'Rubens of philately'. klaseboe.club.fr/sperati.htm
Most stamp forgeries are worth LESS than the genuine stamps they copy. Jean Sperati is the main exception to this general rule. As far as I am aware there were only four Sperati reproductions that came from this part of world. They all sell for MORE th www.glenstephens.com/snapril04.html
The definitive Wikipedia entry for Jean de Sperati. Wikipedia is the biggest multilingual free-content encyclopedia on the Internet. en.wikipedia.org/wiki/Jean_de_Sperati