Customs Seal, British, Customs and Excise, Image & Found by Eddie T-Hunter.
Found in Northern Ireland, ?mm.
Crown // CUSTOMS curving downward / AND / EXCISE
On one side is the British crown and on the other the phrase CUSTOMS (curved around the top) AND (straight across the middle) EXCISE (straight across the bottom).
A U.K. customs & excise seal.
The Tudor crown indicates it is from a date before 1953 - Wikipedia.