"Coining"

Cao gio is a technique incorporated into the practice of traditional Chinese medicine and is better known in English as coining. Coining begins with a massage using a warm oil that is mixed with warming essential oils. Some practitioners use Tiger Balm or another warming ointment. The goal of the oil is to irritate the skin slightly, warming it for the next stage of the process. The massage also relaxes the patient, bringing him or her into a state of centered stillness so that the next segment of the treatment will be more effective.

The coining treatment continues as a coin is repeatedly rubbed against an area of the skin in long flowing moves which always move away from the heart. Blood begins to rise to the surface of the skin, and will leave a mark that resembles a bruise The areas of the body that are most frequently treated are the back and ribs, and the marks will fade a few days after the treatment is over. Coining is designed to bring balance to the body. 

Text and image from Deformutilation, where there is a gallery of a dozen additional images.