3" in diameter.  Designed by US Mint and Hal Reed - marked HR.  Smooth on rim.  
 
Manufacturer: United States Mint (struck at the Philadelphia Mint with no mint mark)Composition: 90% copper and 10% zinc (bronze)Diameter: 3 inches (76.2 mm)Designer: Hal Reed (supervised by Mint Chief Engraver Frank Gasparro)Authorization: Public Law 94-117, enacted October 17, 1975Design DetailsObverse (Front): Features the eagle, globe, and anchor emblem of the Corps superimposed over a depiction of the first major action of the Continental Marines—the landing at New Providence in the Bahamas on March 3, 1776.Reverse (Back): Depicts a modern Marine in action, symbolizing the ongoing tradition of readiness, loyalty, and esprit de corps maintained since 1775.