CREATE TABLE table_21127 ("English name" CLOB, "Irish name" CLOB, "Numeral" CLOB, "Reverse" CLOB, "Introduction" CLOB, "Withdrawal" CLOB, "\\u00a31 Fraction" CLOB)

What date was the 6d introduced?
SELECT "Introduction" FROM table_21127 WHERE "Numeral" = '6d'
SELECT "Introduction" FROM "table_21127" WHERE "Numeral" = '6d'