Made in Ireland by Amethyst of Dublin
 
The simplest of Celtic Knots symbolizing a triune God. For the Celts everything came in threes, maid, mother, crone & the three elements earth, fire and water. 
Christianity embraces this knot to symbolize the Father, Son, and Holy Spirit in many of the early Christian illuminated manuscripts such as the Book of Kells.
The use of the Trinity knot in Jeweler design is associated with eternity and eternal love.