The male lead in the recent romance/tragedy Atonement served in the British Army and was at Dunkirk. Anyone recognize the cap insignia? Did it/does it really exist?
I thought it might be the Royal Sussex, but it doesn’t look quite right.
The brown paper thing is a gas detector paper worn as a brassard. These things were supposed to change colour in the presence of gas. You see them to an extent in 1939-40 as both sides were braced for chemical warfare at this point. Later on most anti-gas equipment was discarded, although it was all issued again for the invasion in '44.
Just took another, closer look at the Atonement DVD, and you’re right. There’s a closeup of Robbie Turner at the 0:56 mark, just after Cecilia shows him the postcard of the seaside cottage, and on his cap you can clearly the two-toned badge shown in the left-side image of the link below. Two minutes later, at 0:58, when Cecilia drops her letter in the postbox, you can see it’s addressed to Robbie in A Company, 1st Battalion, Royal Sussex Regiment, BEF.