Dernière Volonté (last will in French) is a French neofolk project around Geoffrey Delacroix. Delacroix started it in 1998 with a cassette tape published in 120 copies. It would not be surprising to me if he did the copying himself. Immortel is from a bit later, and in the meantime the band has changed its style several times. On this album his music can best be described as synth pop mixed with atmospheric soundscapes.
Inside the gatefold is a hidden 45rpm 7″ single. It is single sided, with the B-side totally empty. The catalogue of this band has a lot of albums like that. According to the French wiki page there were 800 copies, but if they’re not numbered on the sleeve itself, there is no way to verify that.