The website of France’s patent office l’INPI (Institut National de la Propriété Intellectuelle) includes a searchable 19th century patent database. The documents contained within it are scans of the original handwritten documents.
A search for 19th century French fountain pen patents (called variously plume à reservoir, stylo-plume, stylographe, plume sans fin, plume perpétuelle, plume éternelle or plume auto-alimentée) returned two patents granted to the same inventor: Victor Adolphe Valory.
Monsieur Valory was a jewelry maker residing in Caen, and then in Paris, France.
The first patent, FR7007, titled Genre de plume dite Stylographe, was filed January 3, 1848, and granted for 15 years on March 13, 1848 by the Ministry of Agriculture and Commerce. The handwritten leaflet contains 8 pages.
Below, a copy of the top of the first page, and the figure drawing of the mid 19th century, metal-nibbed fountain pen, termed "Genre de Plume dite Stylographe" included in landscape format as page 7 of the leaflet.
Some (possible) very labor-intensive deciphering and transcription of the handwritten patent document is required to understand the details of the disclosure of this invention, whose record can be treasured, and perused, almost 200 years later. Take a peek at FR7007, here!
INPI - 19th century database
INPI - FR 7007