The Standing Liberty Quater was in circulation from 1916 - 1930 and was the result of a competition design by Hermon Atkins MacNeil. The resulting design has Liberty carrying an upraised sheild, an olive branch in her right hand and the only coin featuring Liberty to bare her breast.
Although the1916 version was passed by the US Mint, a newer version of the coin was designed in 1917 holding a number of design changes. The most notible one was Liberty with her previously exposed breast now covered. The coins pre 1925 had a design fault which allowed the date to be worn away and the higher grade coins of the period fetch some of the highest prices for a US coin.
En/wikipedia.org/wiki/standing_liberty_quatre
The round you see here is a replica of the 1916 version with the breast exposed. It is made of .999 fine silver weighing 1 troy ounce, is 39mm in diameter, and 3mm in depth.