It is the plain manzanilla olive without stone.

The plain manzanilla olives of Seville are considered the best olives in the world and the most well known ones in national and international markets.
A small to medium size olive, that is greenish brown in color and oval shaped. It is brine-cured and has firm textured meat providing a slight almond flavor and may be a little bitter or smoky tasting. Generally pitted, this olive is often stuffed with garlic or pimento. Also known as a Manzanillo or Spanish olive.
Sources: Aceitunas Barruz & Food.com