Silbury Coins
A plack, also known as a plak, is a Scottish coin valued at four Scottish pennies. Originally composed of billon,[a]Billon is an alloy of gold or silver with a base metal such as copper. later of copper, it was minted from about 1470 until the union of the Scottish and English crowns in 1603,[1] when the Scottish pound was fixed at one-twelfth that of the English, making a plack the equivalent of an English farthingBritish coin with the value of one quarter of an old penny, 1/960 of a pound sterling..[2]