This is a name plate and member card found in the case of a Holton 'Rudy Wiedoeft' alto saxophone.
Ariel Mattioda was a saxophonist who was a member of the American Federation for Musicians (AFM) back in 1943. AFM is a union for professional musicians from Canada and The United States that was founded in 1896 and still stands today.
The instrument itself is in original gold plate. Rudy Wiedoeft was a virtuoso saxophonist of the era who was well known for his rapid articulations and playing style, and this is his signature model alto saxophone by Holton. A fine vintage instrument, this particular one still bears about 90% of its original gold plate. It has had a complete repad, new neck cork, a bell alignment and is ready to play.