Smith's Dictionary
The rendering “pieces of gold,” as in (2 Kings 5:5) is very doubtful; and “shekels of gold”) as designating the value of the whole quantity, not individual pieces is preferable. Coined money was unknown in Palestine till the Persian period.
International Standard Bible Encyclopedia
The word "pieces" is supplied in 2Ki 5:5 (story of Naaman), "6,000 pieces of gold," where the Revised Version margin more correctly suggests "shekels" (compare 1Ki 10:16).
See MONEY.