Pin has some minor oxidation/patina as seen.

Era Post-WWII / Mid-Century (c. 1950s)

Material Brass (Die-Struck)

From the internet research:

Possibly from the Organization of the US Military Academy (West Point) "Hellcats"

The insignia described is the Military Musicians Arm Badge (also known as the Lyre Badge), which features a lyre (often mistaken for a harp) enclosed in a laurel wreath. This badge was worn by military bandsmen in the British Army and other Commonwealth forces during World War II to denote their role as musicians rather than combatants.

Key details regarding this specific item include:

Design: The badge typically consists of a brass or nickel silver lyre centered within a laurel wreath. It was often worn as a shoulder title (arm badge) on the upper sleeve, though variations existed for headgear.

Usage: It identified personnel in military bands and orchestras, distinguishing them from infantry or other branches.

This one was made in England: Origin: Items marked "Made in England" or "England" were produced by British manufacturers to supply the armed forces during the war. Mount Type Dual Butterfly Clutch (Pin-back)

The dual-post pin-back and butterfly clutches are missing.

GRA