MuMa is gradually publishing the collection database on a dedicated web portal.
You can already consult some of the works:

To date, 900 cards are already present including the complete works of Eugène Boudin (350 cards), Raoul Dufy (128), Edgar Degas (48), Henri-Edmond Cross (41), Albert Marquet (36) and Othon Friesz (27). The portal is enriched each year, in connection with temporary exhibitions and authors who fall in the public domain.