BB& B made distinctive unit insignia in excellent condition in gilt and enamel.
Bailey, Banks, & Biddle, Philadelphia made distinctive insignia for the 510th Coast Artillery. Formed in 1922 as an anti-aircraft unit in Pennsylvania; redesignated as a regiment (AA) in 1924. In the early part of WWII this unit was classified as a Semi-mobile unit of AA, at Fort Sheridan, IL. In WWII broken down into battalion sized units.
This high quality jeweler made insignia was featured in the 1928 BB& B catalog; an early interwar piece.