Halfpenny (Irish decimal coin) particularly rare, and valuable to coin collectors - the vast majority of the 2.8 million were melted in 1987. The 1986 coin was only produced for the 1986 specimen sets and is also rare. Halfpenny (Irish decimal coin) The decimal halfpenny (p) () coin was the smallest denomination of the Irish pound. It was first issued when the Irish currency was decimalised on Decimal Day, 15 February 1971. It was one of three new designs introduced all in bronze and featuring ornamental birds on the reverse. The coin value was weakened by inflation and very few were produced beyond the
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