"Lupin III: Secret File" is actually a compilation of remastered version of the Lupin III: Pilot Film and four film trailers. The trailers are for the first four Lupin films: "Lupin vs. the Clone", "Castle of Cagliostro", "Legend of the Gold of Babylon" and "The Fuma Conspiracy".
In 1989 "Lupin III: Secret File 2 - Sound Collection" was released consisting of openings and endings of all previous Lupin series and theme songs.
(Source: AniList.co)