After searching again, I can confirm it's a factory early fretless Passion II (introduced in 1985) with a graphite neck and a phenolic fingerboard as, like all the early ones, it has a real bone nut, no dots on the front and white fret lines when the fretted versions of that period had no front dots too and a zero fret, so a converted one would still have it or something even weird(er) with a huge nut...
Check this review (by the great Tony Bacon) from ... 1985, everything matches: https://www.muzines.co.uk/articles/vigier-passion-bass/11761
Remember that the Passion (introduced in 1983) came after the Arpège (introduced in 1980) and was thought differently, but here is the rare beast @itu, a 1983 Passion I fretless with a Delta Metal fingerboard and a graphite neck without truss rod, of course: https://www.basscentre.com.au/products/vigier-passion-fretless-1983
You can even compare this Passion II fretless with its fretted sibling here: https://www.leboncoin.fr/vi/2887220561.htm#xtor=ES-3999-[MYSRCH]
Hope all this helps. 😉
GLWYS!