The Soleau envelope (French: Enveloppe Soleau), named after its French inventor, Eugène Soleau [fr], is a sealed envelope serving as proof of priority for inventions valid in France, exclusively to precisely ascertain the date of an invention, idea or creation of a work.
The working principles were defined in the ruling of May 9, 1986, published in the official gazette of June 6, 1986 (Journal officiel de la République française or JORF), although the institution of the Soleau envelope dates back to 1915.
[3] The envelope may not contain any hard element such as cardboard, rubber, computer disks, leather, staples, or pins.
[2] Unlike a patent or utility model, the depositor has no exclusivity right over the claimed element.
The Soleau envelope, as compared to a later patent, only allows use of the technique, rather than ownership, and multiple people might submit envelopes to support separate similar use, before a patent is later granted to restrict application.