This vintage sterling silver charm is not marked sterling that I can see. I did not remove it from the card- I do have another of these and I acid tested it and these are sterling charms. They are also two sided bubble charms and measure approximatley 1/2 inch tall without the bail.

The front design is two unicorns with a tulip which is the symbol of virtue and piety. The tulips in the design are for faith, hope, and charity. (information from Hexology by Jacob & Jane Zook copyright 1962)