A stamp commemorating the estimated six million Irish emigrants who left Ireland for the US was issued yesterday on both sides of the Atlantic by An Post and the United States Postal Service. The Minister for Public Enterprise, Ms O'Rourke, unveiled the Irish stamp, which comes in a 45p denomination, at a ceremony at the Queenstown Heritage Centre in Cobh, Co Cork, from where most Irish emigrants to the US departed. The US version of the stamp, in a 33-cent denomination, was later unveiled at a separate ceremony at the Kennedy Library in Boston.