Instead of a specialist unit within the SD, prisoners from Nazi concentration camps were selected and sent to Sachsenhausen concentration camp to work under SS Major Bernhard Krüger. The unit produced British notes until mid-1945; estimates vary of the number and value of notes printed, from £132.6 million up to £300 million. By the time the unit ceased production, they had perfected the artwork for US dollars, although the paper and serial numbers were still being analysed.