This is a vintage Boys' Brigade One Year Service badge. 

It is a diamond-shaped, die-stamped badge, often found in chromium-plated or nickel material. 

The design features the 'Sure & Stedfast' anchor emblem with a cross behind it. 

This specific style of badge with the cross behind the anchor was used post-1926. 

It is a collectible item related to the Christian youth organization, The Boys' Brigade, founded in Scotland in 1883.