Penny (Irish decimal coin) Penny (Irish decimal coin) The decimal one penny (1p) () coin was the second smallest denomination of the Irish pound. It was first issued when the Irish currency was decimalised on Decimal Day, 15 February 1971. It was the second of three new designs introduced all in bronze, the others being a half-penny and a two pence coin. All featured ornamental birds designed by Irish artist Gabriel Hayes on the reverse. The coin originally had a diameter of 2.032 centimetres and mass of 3.564 grams consisting of copper, tin and zinc. This was identical to the British decimal penny as
Decimal fractions. The Egyptian hieratic numerals, the Greek alphabet numerals, the Hebrew alphabet numerals, the Roman numerals, the Chinese numerals and early Indian Brahmi numerals are all non-positional decimal systems, and required large numbers of symbols. For instance, Egyptian numerals used different symbols for 10, 20, to 90, 100, 200, to 900, 1000, 2000, 3000, 4000, to 10,000. The world's earliest positional decimal system was the Chinese rod calculus. Decimal fractions were first developed and used by the Chinese in the end of 4th century BC, and then spread to the Middle East and from there to Europe. The written Chinese