This is a 3D printed Celtic knot necklace. The two interlocking knots represent mother and child. It is made from gold-plated stainless steel and is about 1.5" in length. Buy this pendant on Shapeways: shpws.me/oT1x
Actually, my favorite finish on the stainless steel is the "antique bronze". It is shown on the piece in my avatar. It is very "steampunk". When it is on the right item, it looks natural and really neat. But a lot of people don't like to wear darker jewelry like that, so the gold is more popular.