Stamps of PANAMA
According to Varro Tyler's Philatelic Forgers, Their Lives and Works, Fournier, unlike many of his contemporary forgers, did not seek to defraud the public.  He described his material as facsimiles and promoted it to collectors who could not afford to purchase genuine items and to uneducated collectors as a preventive measure against being deceived by dishonest stamp dealers.

When Fournier died in 1917, one of his employees, Charles Hirschburger, unsuccessfully tried to continue the business.   When Hirschburger died in 1927, l'Union Philatelique de Geneve purchased the Fournier stock, which weighed over 800 pounds, from Hirschburger widow.  The Union then marked the forgeries with "FAUX" handstamps on the front and/or "Facsimile" on the reverse, and employed students from the Geneva School of Arts and Crafts to mount representative selections of the forgeries in 480 albums.   Whatever was not placed into one of the books was burned to ashes.

Because Fournier made forgeries from such a wide variety of countries, many of the 480 books have been either been divided into country references or have had many items removed.

As you can see here the 10c and 20c have the "FAUX" cancel.  The 5c does not have the cancel, but you can definitely tell the similarities between them.
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