USA Meat Seal, Image by StuE, Found by Dangerous Dave.
Found in the Colchester area. 13mm. 3.1g.
Small seal with US[A?] on one side with a bar above and possibly one below. Above curved around an indent is the word PATENTED. The other side has a bar above and below the word [M]EAT. Part of the M is missing due to a void that appears to lead to a cavity containing the attachment wire - there is a nodule of rust on the outer edge adjacent to the void.