Shekel

Boyd’s Bible Dictionary:

(weight). A weight for weighing uncoined money, of Assyrian and Babylonian origin. There seem to have been two standards, that of the sanctuary and the king (Ex. 30:1313This they shall give, every one that passeth among them that are numbered, half a shekel after the shekel of the sanctuary: (a shekel is twenty gerahs:) an half shekel shall be the offering of the Lord. (Exodus 30:13); 2 Sam. 14:2626And when he polled his head, (for it was at every year's end that he polled it: because the hair was heavy on him, therefore he polled it:) he weighed the hair of his head at two hundred shekels after the king's weight. (2 Samuel 14:26)). Both approximated half an ounce, valued in silver at about 64 cents. Later, a Hebrew silver coin, with bronze half and quarter shekels. Probably the “pieces of silver” (Matt. 26:1515And said unto them, What will ye give me, and I will deliver him unto you? And they covenanted with him for thirty pieces of silver. (Matthew 26:15)), though the “pieces of silver” in Luke 15:88Either what woman having ten pieces of silver, if she lose one piece, doth not light a candle, and sweep the house, and seek diligently till she find it? (Luke 15:8) are clearly the Greek drachmas. The first Jewish coins were struck by Simon Maccabeus, who obtained permission to coin money from Antiochus, King of Syria. His shekel showed a vase on one side, representing a pot of manna, and on the other an almond branch with flowers, representative supposedly of Aaron’s rod.

Concise Bible Dictionary:

From Manners and Customs of the Bible:

1. What the “shekel of the sanctuary” was is not definitely stated. There are those who think it was worth double the value of the ordinary shekel. Others, again, suppose that “the shekel of the sanctuary” was the standard to which all shekels must conform if of full weight. See note on Genesis 23:1616And Abraham hearkened unto Ephron; and Abraham weighed to Ephron the silver, which he had named in the audience of the sons of Heth, four hundred shekels of silver, current money with the merchant. (Genesis 23:16) (#26).
2. The gerah was the smallest weight known to the Hebrews, and the smallest. piece of money used by them. It weighed between eleven and twelve grains, and was in value about three cents.