British MRC Body Armour

Developed by the British medical research Council between 1940 and 1942 to equip frontline troops, issued in April of 1942.
1mm manganese steel - equivalent to a Brodie helmet, 1,6kg, three parts, covered in canvas. Protects from .38/200 rounds at 5m, from .45ACP rounds from a Thompson submachinegun at 90m and from .303 British rounds at 640m.

Although the initial order for this armor was originally of 500000 units, only 200000 were made and 72000 issued due in part to the materials being used in priority to manufacture helmets, and because there were found, “although well padded, [that they] tended to cut into the soft-skin areas of the body causing chafing, with the result that violent and rapid movements were significantly impaired. Moreover, it causes a man to perspire so profusely that his powers of endurance were affected.” - Simon Dunstan, Flak Jackets 20th Century Military Body Armour.
Their use although perhaps not as efficient as intended still gave soldiers a boost of confidence when part of the first line of assault, and the armor was used in majority by airborne forces of the RAF. This all took place in parallel with the private development of the Wilkinson M1 Flak jacket that was issued in 1943.

pictured thusly.