This is the Sead of Life pendant.

The "Seed of Life" is formed from seven circles being placed with sixfold symmetry, forming a pattern of circles and lenses, which act as a basic component of the Flower of Life's design.

The Seed of Life is a symbol supposed by the New Age community to depict the six days of creation in which the Judeo-Christian God created life; Genesis 2:2-3, Exodus 23:12, 31:16-17, Isaiah 56:6-8. The first day is believed to be the creation of the Vesica Piscis, then the creation of the Tripod of Life on the second day, followed by one sphere added for each subsequent day until all seven spheres construct the Seed of Life on the sixth day of Creation. The seventh day is the day of rest, known as the "Sabbath" or "Shabbat."

Dimensions:

It's diameter is 0.9 inches / 23mm.
Comes with an adjustable waxed string.
Cast from brass.