Stamp Duty was introduced to Ireland in 1774 and initially the duty stamps were embossed directly onto the documents by dies. In time it became the practice to provide separately embossed stamps, commonly using a thick blue paper, and glued onto the document.
In order to ensure the stamp was securely attached to the document, the stamp and document were modified by cutting two small slits through both, into which a thin strip of tin was inserted before the embossing operation. The resulting impression can be easily seen in the tin. The ends of the strip were folded under and covered on the underside of the document by thin paper seals known as cypher labels. These bore the initials of the reigning monarch and are now collectable in their own right.