Stater
Easton's Dictionary
Greek word rendered “piece of money” (Matt. 17:27, A.V.; and “shekel” in R.V.). It was equal to two didrachmas (“tribute money,” 17:24), or four drachmas, and to about 2s. 6d. of our money. (See SHEKEL.)
Smith's Dictionary
[Money]
International Standard Bible Encyclopedia
sta'-ter (stater): Used only once, Mt 17:27, where it is rendered by "piece of money" in the King James Version and "shekel" in the Revised Version (British and American). It was originally a standard Greek weight equal to two drachmas, but later it was used to designate the tetradrachma, and this is probably the coin referred to in the above passage.
See MONEY.