This is a sterling silver or gold chain that has the Hebrew letters YHVH on it. These letters spell the name of Yahweh in Hebrew. It is a very significant and meaningful chain proclaiming the name of Yahweh.
"Ascribe to Yahweh the esteem of His Name; Bow yourselves to Yahweh in the splendour of set-apartness." (Psalm 29:2)
The chain is 47cm long. The word is 2cm long and 0.8cm high.