As aforementioned the closure is a zipper system along with  popper buttons / studs

This particular jacket would've belonged to a member of the British army's Royal Military Police

with "Size 1" labelled inside rather than the NATO friendly current labels

Ribbon Bar Includes

British Army No.2 FAD Dress Jacket - Royal Welsh Dress As aforementioned the closure isAt a glance 100% Wool Material 2 Button Chest Pockets, 2 Flap Hip Pockets & 3 Internal Slit Pockets Button Closure Beautiful Engraved Golden "Staybrite" Buttons Featuring The Royal Welsh's Insignia Signaller Trade Badge Patch Lance Corporal Rank Sleeve Patches Belt Loops Shoulder Epaulettes "Solid Barracks Brown Colour" Current Issue "FAD" Future Army Dress Design Chest Size: 36" Small Slim Label states 84cm and a waist of 72cm Sleeve Length: 26" Long