"Marlag and Milag Group."
Wikipedia states that Marlag and Milag Nord was a dual-purpose German prison camp: the Marlag imprisoned Royal Navy personnel while the Milag was for merchant seamen, such as James Swinnerton, seen in this photograph third from left, front row. The uniforms seen in this photo make the Marlag/Milag personnel distinction obvious.
Swinnerton was a member of the British Merchant Navy that shipped supplies to Allied troops during WWII. In March of 1940, his ship, called "The Salmon Pool" which made trips from Norway to Britain, was attacked by Germans while just offshore in Norway. The British seamen jumped off the ship, swam to shore where the Germans were waiting for them. The seamen were then taken to the Milag section (an acronym for "Marine Internierten Lager" (Marine Camp Internees) of the prison camp the inmates referred to as Steinburg, located near Westertimke, Germany, where they remained for the duration of the war.
Swinnerton was given this photographic memorial book by one of his fellow prisoners at the war’s end. Photos appear courtesy of Alison Madden, Swinnerton's granddaughter and author of the children's book, "Fred and Fiona Flea and the Crown Jewels Caper."