Antique WW1 Soldier’s Collapsible Vest Pocket Cup. It has a steel rings that pull out to form a cup and collapse to fit neatly inside a brass top and base. This compact and portable cup served as a practical solution for soldiers to stay hydrated while on the move or in the field . Typically made of durable metal such as aluminum or stainless steel, the cup could easily fit into a soldier's uniform pocket.