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 approximately 9/16ths inch tall without the bail.
The front design is called Trinity Tulips. The back is a blue bird or distelfink. The trinity tulips signify faith in yourself, faith in what you do, and faith in your fellow man. They also signify faith, hope, and charity.(information from Hexology by Jacob & Jane Zook copyright 1962)This item may be available in our Etsy Store