Vintage 1940s "Airman" shirt collar.
This is genuine wartime "utility" clothing, made during the time of clothes rationing in Britain (1941-1949).
These collars were stamped with the official CC41 Utility mark.
During the Second World War, there were restrictions on garment design, to minimize waste, and to ensure that resources could be concentrated on providing necessary supplies for the troops, together with a basic standard of clothing for civilians. The CC41 mark showed that these garments conformed with wartime economy standards.
Rationing was also in force - people wanting to buy the utility clothing, would have had to use their clothes ration coupons (as well as paying for the garments).
This was to ensure that everyone had an equal chance of buying necessary clothes, and to prevent hoarding and profiteering.