British Royal Engineers uniform button, specifically a "Staybrite" button featuring the EIIR cypher (Elizabeth II) and a Queen's crown.

1" Made by Gaunt London

This type of button was used on the No. 2 Service Dress uniform of the British Army, particularly by the Royal Engineers.

"Staybrite" refers to a type of anodised aluminum used for military buttons, known for its durability and resistance to tarnishing, eliminating the need for polishing.

The EIIR cypher indicates the reign of Queen Elizabeth II, dating the button to her period of rule (1952-2022).

These buttons were often used on jackets and other parts of the No. 2 Dress uniform, which was worn for formal and general duties.